Every driver who races single-seaters aspires to reach the pinnacle of the sport, Formula 1. The vast majority of them will fail, many because they simply aren't good enough to earn a place.
Others do have what it takes but fall by the wayside for myriad reasons, be it insufficient funding, lack of opportunity, injury and, in a few thankfully increasingly rare cases, death.
There are many drivers who would have done a competent job in F1, fewer who would have done a good job and fewer still a great job, but who are they?
AUTOSPORT has decided to answer this question once and for all. The criteria are simple. All drivers who have not started a world championship race (excluding the anomalous points-paying Indianapolis 500s of 1950-1960) are eligible.
Drivers from all disciplines were considered, with an emphasis on those with serious single-seater aspirations over those who 'merely' excelled in a particular branch of the sport - apart from those currently climbing up the racing ladder.
Not happy with our list? Let us know your thoughts by emailing us at: firstname.lastname@example.org
50 VALENTINO ROSSI
Ferrari boss Luca di Montezemolo claimed he would have fielded Valentino Rossi in a third car had the rules allowed it after the Italian impressed in tests.
The nine-time motorcycle world champion gave it serious thought but decided against trying to emulate John Surtees.
49 BIRD CLEMENTE
Regarded by some as the most talented Brazilian driver of all time, Bird Clemente's reputation remains confined to the memory of those who had the chance to watch him at work.
Undisputed master of the four-wheel drift in the underpowered Brazilian version of the Alpine A108 (named the Berlinette Willys Interlagos), it was the only way its driver had a chance against the monstrously powerful V8 Corvette engines on the 'carreteras'.
The lead driver in 'Equipe Willys', a team that had Emerson and Wilson Fittipaldi and Carlos Pace in its junior ranks, Bird had too much to lose to follow the 'kids' in their European adventure.
"In those days, to race in Europe was not viable, at least for me," he recalls. "I had a wage as a professional racing driver but still I had to run the family business with my father. I was not as young as Pace and the Fittipaldi brothers, and I was married so I'm not sure it would have had a happy end!
"Many times Moco [nickname of Jose Carlos Pace] invited me to Europe with him, he wanted to introduce me 'to the right guys', but my time had already gone by."
Those who saw Clemente hard at work, sliding the nimble Berlinette through the corners of the magnificent old Interlagos circuit, are sure that F1 lost out without such a talent on its grid. Just ask Emerson Fittipaldi about him...
48 CARLOS SAINZ
Sainz was an all-round sporting hero who excelled at squash and is reputed to have had a trial with football giant Real Madrid. His single-seater career didn't get beyond Formula Ford 2000, but there is evidence to suggest he could have gone much further on the race circuits, rather than rally stages, of the world.
During his second stint with Toyota's WRC squad he got the chance to test its GT-One Le Mans 24 Hours contender at the Circuit de Cataluyna, and impressed at least one onlooker — a certain Allan McNish.
"I was [standing] out on the circuit at the end of the day, and the Toyota went past," remembers McNish, who was there testing for Porsche. "I remember thinking to myself that [Martin] Brundle was going quickly. But when I got back to the pits, I found out that it had been Sainz in the car.
"I seem to remember that he was less than a second slower than Brundle after just two-thirds of a day in the car. That was impressive given that at the beginning of the day, I'd followed him and he could barely drive the thing in a straight line. The steering in that car, as I would find out the following year [when he moved to Toyota], was so direct."
47 NICOLAS MINASSIAN
Runner-up spots in both French and British Formula 3 and multiple victories in Formula 3000 suggest that Nicolas Minassian should have made it to F1 but his two test outings, in truth, were never going to lead anywhere.
The Frenchman landed a test with Williams at Barcelona after finishing second in the British F3 series with Promatecme in November 1997. But there was a problem.
"I had broken a knuckle at Macau and I was told that I probably shouldn't do the test," he recalls, "but when you get an opportunity like that you have to take it."
He reckons the two test deals on offer were preordained for Juan Pablo Montoya and Max Wilson anyway.
Minassian's other test came with the abortive Honda F1 project, masterminded by Harvey Postlethwaite, at Pembrey in 1999. That team, of course, never made it to the grid. There were also talks about going to Minardi for 2001, but he has no regrets today.
"All I know is that deep inside, I know I was good enough for F1, and that's good enough for me," he says. "I raced against good people like Montoya, Mark Webber and Fernando Alonso and was always a race-winner."
46 JAMES COURTNEY
On July 11 2002, the future looked bright for James Courtney. He led the British F3 championship and was having another test outing for the Jaguar F1 team. Then, approaching the Ascari chicane at Monza, the rear wing collapsed, taking out the right-rear suspension and pitching the car into the wall at north of 180mph.
"That shunt fundamentally changed his outlook on F1," says Alan Gow, Courtney's long-time manager. "He had nerve damage on his right side but after he'd been to the medical centre to check there were no broken bones, the team gave him a couple of Nurofens and put him on an EasyJet flight. That's when he decided he wasn't going to be cannon fodder for anyone and we didn't pursue F1."
Courtney, who lost out on the British F3 title to Robbie Kerr after missing the Rockingham round, won the Japanese title a year later and after three years racing professionally in Japan, switched to V8 Supercars.
"He wanted to be a professional driver in a good car in a good series and that's what he's doing," says Gow.
45 ANDY WALLACE
Andy Wallace had a sniff of a Formula 1 seat in the wake of his successful second season of F3 in 1986. Straight after victory in Macau, he got the chance to try-out for Benetton at Donington Park and impressed some in the team to push for a race seat for him for 1987.
The vacancy went to Thierry Boutsen, and Wallace wouldn't drive an F1 car again until he started testing for Leyton House in 1990. He was officially the team's test and reserve driver for two seasons, but by then he was already an established star of the sportscar world.
What was it like to jump from an F3 car to a 900bhp F1 Benetton?
It was a bit of baptism of fire and the power blew me away because it came in so quickly. You had to change up at 11,000 or 11,500rpm and for the first few laps I was hitting the rev limiter, even though I was changing up when I saw 8000 revs on the dash.
How quickly did you go?
There were a lot of drivers there, and I know Emanuele Pirro, who was straight out of F3000, was quickest, and I was second quickest.
Was there a chance of racing for Benetton?
There wasn't much communication about my prospects, so I don't really know. I always thought that with a bit of F3000 experience, I would have had a better shot at it. I did get offers from Tyrrell and Arrows for the following year, but they both needed money and I ended up going to F3000.
44 ALAIN FERTE
The Ferte brothers were two of the brightest stars of French motorsport in the early to mid-1980s.
They won the Monaco F3 race three times between them and were both French F3 champion, yet neither of them made it to the grand prix grid.
Which was most deserving of a shot at the big time? Hugues de Chaunac, whose ORECA team ran both of them, is best placed to make the call.
"Michel was the more talented, but he wasn't hungry enough," he says. "Alain was very talented also, but he had more desire and the better approach."
43 GARY HOCKING
When Gary Hocking, born in the then-Rhodesia in 1937, lost his life in a crash in practice for the 1962 Natal Grand Prix, it came, ironically, after he had turned his back on motorcycle racing over its dangers.
He had impressed so much in his brief car racing career that he was seen as having the potential to be a winner at the top level.
At the time of his death, driving a Lotus 24, he was entered for the following week's South African GP at East London, a race that might have marked the start of something big.
42 CHRISTOPHE BOUCHUT
The nearest Christophe Bouchut got to F1 was an abortive deal to race for the Larrousse team had it managed to make it onto the grid in 1995. But you'll find a queue of people - both friends and foes - willing to tell you that the Frenchman had everything to succeed at the highest level.
"He had the selfishness, the arrogance and the animal instinct to succeed in F1," says one nameless former rival in both single-seaters and sportscars.
Bouchut's chances of making it to F1 went off the rails after a winning campaign in French F3 with Graff in 1991 when he fell out with Marlboro.
It wasn't all bad news for the Frenchman. He fostered links with Peugeot, won the Le Mans 24 Hours at the first attempt in 1993 and went on to have a successful sportscar career.
41 JEAN-PIERRE JAUSSAUD
Jean-Pierre Jaussaud's talents behind the wheel have been compared with those of Jim Clark by no less a luminary than Henri Pescarolo.
A neat and concise driver, he won the French F3 title in 1970 and challenged for the European Formula 2 crown in '72, but he missed the F1 boat and went on to a successful sportscar career that included two victories in the Le Mans 24 Hours.
"Watching him out on the track was like watching Jimmy," says Pescarolo. "He was very clean and never got the car sideways. His problem was that he lacked killer instinct. Maybe he was too nice for F1."
40 CRAIG LOWNDES
After dominating Australian Touring Car racing in 1996, Craig Lowndes arrived in Europe to take on F3000 with the RSM Marko team.
While team-mate Juan Pablo Montoya finished second in the title (behind Ricardo Zonta) Lowndes, then 22, struggled, scoring his only points with fourth place at Enna. By the start of '98 Lowndes was back in Australia to resume what has been a stellar V8 Supercar career.
"I have no regrets," admits Lowndes. "In hindsight, you could always have made better choices, but it showed me what the world of motor racing was like. The only disappointment was that I did not get a second season [in F3000]."
Ironically, he did get to test a Formula 1 car when he and Jenson Button swapped rides at Mount Panorama in 2011. He describes it as a "huge" experience.
39 BERTRAND FABI
Richard Dutton has worked with a raft of young drivers in the junior formulae over the past 30 years. Yet he only has photographs of one at home. They don't feature Juan Pablo Montoya or Heikki Kovalainen, who both used stints at his Fortec team as a springboard to F1, rather another driver who never got the chance.
Dutton puts Canadian Bertrand Fabi right up there with any of his other alumni in terms of talent.
"There's no doubt that Bertrand would have got to F1 in my mind," recalls Dutton, whose Richard Dutton Racing team took over Fabi's British and European campaigns from Penistone Racing for the final races of the season.
"He was naturally quick and was in control of every situation, and he had good backing from Canada.
"He's one of the drivers I've had who really stands out. He's right up there with Montoya and Kovalainen."
Fabi wanted to graduate to F3 with Dutton, but the team boss suggested he go to the ultra-successful West Surrey Racing team.
"I didn't think I was good enough for him to be honest, so I pushed him towards WSR," continues Dutton. "It is one of the biggest regrets of my life."
Fabi never got to start his F3 career. He was killed in an accident in testing at Goodwood in early '86 before his British series campaign could begin.
38 ANDRE LOTTERER
This star of Audi's current prototype line-up, and a world champion to boot, would surely have made the grade in F1 had he got the chance.
The German is also a Formula Nippon champion - and leads this year's rebranded Super Formula series - but his career in Europe foundered after a solo year of British F3, even though he was an irregular tester for the Jaguar F1 team until mid-2002.
Yet the signs of greatness were there during a season in Britain with Jaguar Racing (formerly Paul Stewart Racing) that yielded one win and seventh in the points.
A newcomer to the British circuits, he didn't land the deal until after his rivals had more or less finished their pre-season test programmes, but his engineer, Alan 'Skelly' Woodhead was hugely impressed.
"He was mega in the high-speed corners; he was the first person I can remember taking Copse at Silverstone flat in an F3 car," he recalls. "When he stepped up to bigger, quicker cars racing on circuits that were predominantly faster, his talents shone through even more.
"I've no doubt that had he got to F1, he would have made the most of it and gone on to have a successful career."
37 RICKARD RYDELL
His big chance was arguably in 1991, driving the beautiful new TOM'S car for the Japanese constructor's UK arm in British F3.
It was a vintage season. Experts reckoned he was the only match for Rubens Barrichello on pace, the top two having a slight edge over David Coulthard and Gil de Ferran. But the TOM'S, so fast in the corners, was too draggy on the straights, and its Toyota engine - developed around the fuel used in Japan - was slow in British spec.
Rydell was therefore a sitting duck in races; TOM'S GB said his racecraft wasn't up to scratch, and refused to develop the car. He rather proved the team wrong when he became a king of Super Touring's peak international era with Volvo.
His effortless, fluid, delicate touch put the S40 - never the fastest tin-top - on pole at hang-on-for-dear-life Thruxton and Bathurst by over a second. In the meantime, Rydell's exploits single-handedly fired up Sweden's passion for touring cars that exists to this day.
36 ALAIN MENU
The Swiss won races in French and British Formula Ford, but results were patchy in F3 and F3000.
After moving to tin-tops in the British Touring Car Championship with the Prodrive-run BMW junior squad, he made his way to Renault. This led to a straightline test chance with Williams-Renault in 1993 and, two years later, a full test at Silverstone.
By then, recognised as one of the fastest Super Touring drivers in the world, he showed he had the speed to deliver in an F1 car with an impressive test at Silverstone, particularly in the slower corners.
"I tested at Silverstone two weeks after Jacques Villeneuve," says Menu.
"He was straight out of Champ Car and I hadn't driven a single-seater since 1991 and I was faster at lunchtime than he was at the same point.
"By the end I was maybe six or seven tenths off, which I was pleased with.
"My neck was the problem. I was given five runs and by the third outing it was already gone."
35 KENNY BRACK
Brack was briefly the 1996 F3000 champion and seemingly on the brink of F1.
But stewards stripped him of victory in the Hockenheim season finale for dangerous driving while passing title rival Jorg Muller.
An appeal was unsuccessful and Brack headed to America to seek his fortune, claiming the IndyCar title [then under the guise of the Indy Racing League] in '98 and adding victory at the Indianapolis 500 the following season.
34 NICOLAS LAPIERRE
Alexandre Premat (who deserves an honourable mention on this list) won more races in the winning assault in the inaugural A1GP World Cup of Motorsport with Team France, but team-mate Nicolas Lapierre made the bigger contribution.
That's the verdict of the DAMS-run operation's race engineer, Chris Gorne.
"Alex pipped Nico in terms of race victories [the scoreline was 7-6], but Lapierre was the more complete driver," explains Gorne.
"Nico was as quick as Alex, but he was much better technically. The car was good because of him and part of Alex's success was down to Nico.
"Personally I think he should have made it to F1. He has always been a bit underrated. He deserved a crack at it."
33 JOHN NIELSEN
Nielsen only drove an F1 car once, and then only for demonstration purposes. Yet his run in a Renault RE30B at the Jyllandsringen in 1983 at the behest of the French marque's importer wouldn't have been his sole appearance but for the vagaries of marketing men.
The future sportscar legend was set for the pinnacle of motorsport with a factory Volkswagen team in 1984.
Nielsen's hat-trick of European Super Vee titles in 1979 to '81 had persuaded VW to fund an F3 programme with British tuner Engine Developments and a factory team run by the big Dane.
Success in the 1982 German F3 series led to the decision to go F1 with a VR8 twin-turbo powerplant developed in conjunction with Engine Developments and a chassis built by March. Only it never happened.
"The project had been given the go-ahead, the engine was built and a VW Motorsport department was under construction in Hanover, and then all of a sudden it was stopped," recalls Nielsen. "It was all down to marketing reasons.
"One minute I was going to be an F1 driver and the next minute I wasn't. I had a deal with Ken Tyrrell for 1985, but I couldn't find the US$500,000 I needed.
"That was it for me as far as F1 was concerned. But that's life."
32 JEAN-LUC SALOMON
Salomon was just a week away from his planned F1 debut in the French GP driving a Lotus when he died from injuries in an F3 crash at Rouen.
The 26-year-old was the great hope of French motorsport and surely had what it took to be a success in F1.
"There was no flamboyance in him at all, a very steely character," recalls Mike Knight, whose Volant Shell scheme Salomon won.
"Without doubt he would have made it to F1. We ran him in F3 and he was the most opinionated, stubborn bloke we ever dealt with.
"The following weekend to that F3 race [when he was killed], he was flagged to drive the Lotus in the French Grand Prix. But Tico [Martini, who ran Salomon] and I felt he was being pushed far too quickly.
"There was an enormous dearth of talent in France and they were keen to catch up. They were pushing him very hard when he was killed."
31 PAUL WARWICK
The 22-year-old was dominating the British F3000 championship when he lost his life in an accident at Oulton Park. Brother Derek has no doubts Paul would have made it to F1.
"I 100 per cent believe that Paul would have got to F1 and would have been good enough to win races and the championship. He had already tested for Arrows and made contact with an F1 team for 1991," says Derek.
"Where Paul was clever was he looked and listened to everything I did, discarding the mistakes and building on the positives.
"He trained with me and had already overtaken me on fitness. He realised during his F3 seasons that a steering wheel is not enough, it's the work you put behind it that makes the difference.
"He was very strong mentally, quick and consistent. He desperately wanted to get into F1 and everything he did was to make him a better driver."
30 JORG MULLER
The German won titles in his native Formula Opel and F3 series, as well as in International F3000.
Yet despite consistently impressing in F1 tests with Arrows, Sauber and Williams, he never landed an F1 break.
Seriously fast, the only question mark is whether the affable Muller had the ruthless edge needed to thrive in F1. He went on to achieve success in touring cars and GTs with BMW.
29 GONZALO RODRIGUEZ
Gonzalo Rodriguez was a man out of his time. Had the Uruguayan pitched up in Europe in the 1970s, he would have breezed into F1.
Yet his engineer during his two race-winning seasons at the Astromega F3000 team in 1998-'99 reckons he still should have made it to F1.
"He was the last of a breed, an old-school driver who wasn't interested in training or going through the data," recalls Chris Murphy. "But he was naturally gifted and very strong, both physically and mentally. Just look what he did with us and with Penske in CART.
"He probably came along a bit too late, but there was still room for someone like him in F1 at the start of the '90s, whereas there isn't today."
Free-spirit Rodriguez would almost certainly have been more at home in Champ Car than F1 and, at the time of his death practicing for Penske at Laguna Seca in September 1999, he was on course for a full season in the US with Patrick Racing in 2000.
28 STEPHEN SOUTH
Stephen South has gone down in the history books as a driver who failed to qualify a McLaren in his one attempt at F1. But that does not do his ability justice, for there was no shame in failing to get a McLaren M29 onto the grid at Long Beach in 1980 given that the car was far from one of the team's finest.
Instead, it was what happened in practice for a Can-Am race in Trois Rivieres in Canada about five months later, when he suffered an accident that led to part of his left leg being amputated, that ended what had been a very promising career.
27 SATOSHI MOTOYAMA
Arguably the greatest Japanese driver of his generation. His record of four Formula Nippon titles and three in Super GT speaks for itself, yet he was barely on the F1 radar even in his pomp.
That's not surprising given that his only race appearances in Europe were his three starts in the Le Mans 24 Hours.
There was a one-off outing as a Friday tester with Jordan at the 2003 Japanese Grand Prix at Suzuka, and a test with Renault a few months later, but could he have made it in F1? Ricardo Divila, who worked with Motoyama at the Impul team during the noughties, isn't so sure.
"He always seemed to be a bit of a fish out of water when you took him out of the environment he was used to," Divila says. "Like many Japanese drivers, he didn't travel well, but he was bloody fast in Japan."
26 JASON WATT
One of the brightest stars of the 1990s, Jason Watt's career ended on the verge of Formula 1, when he was paralysed from the chest down in a motorcycle crash.
"David Sears was my manager," he recalls. "We had contacts with Benetton and Prince Malik at Arrows! I also had a meeting with Bernie Ecclestone at Monaco. We were trying to use the me-being-coloured thing as a way to stand out.
"We met Pat Symonds at Benetton - at the time they had the 'United Colours of Benetton' slogan. They offered me a test drive, and I remember that they couldn't guarantee any driving. My backer at the time - Den Bla Avis - was given the price of around $2m, but because they couldn't say how much time I would get we backed out of that.
"We had a meeting with Malik at Imola and he was saying how he needed a black driver for F1. I thought that was my way in, then suddenly he disappeared.
"Then after my accident, Sears came to see me and said, 'that was bad timing mate, you had the Williams test coming up'. That was the closest I came to F1.
"Bruno Junqueira I beat on a regular basis in F3000, and who the hell was Jenson Button? Some guy in F3. I thought I could beat him easily. At the time I was convinced that seat had my name on it.
"Sometimes I think I could have made a career out of F1, but I have the obvious answer why not. It must be harder for someone like Tom Kristensen to understand why he didn't get the chance."
25 TONY STEWART
Tony Stewart never made it on to the F1 radar, but he certainly had the potential.
He did get to sample one of the great F1 cars of recent years. On a damp, cold June morning at Watkins Glen, Stewart managed a handful of laps aboard Lewis Hamilton's 2008 title winner.
Conditions rendered times meaningless, but Stewart's commitment was mightily impressive.
"I'm glad I didn't know what these cars were like 20 years ago because I may not have put a fender on a race car after that," he said, still beaming after half a dozen laps in a car the polar opposite of a 3400lb stock car.
24 PAUL TRACY
Paul Tracy was the latest hotshoe in the US CART Indycar series for Penske when Flavio Briatore invited him to test for his Benetton squad at Estoril in 1994.
The Canadian turned in a very impressive performance, ending up just seven-tenths of a second off Gerhard Berger's pole position time for the recent Portuguese GP.
His lap of 1m21.29s was quicker than both Benetton drivers, Jos Verstappen and JJ Lehto (subbing for the banned Michael Schumacher) had managed in qualifying for that race.
Tracy was offered a deal for '95 (subject to permission from Roger Penske to get out of his contract) and there was also the possibility of making the move in 1996, but ultimately Tracy decided his long-term future lay in America, partly because of a lack of assurance he would have the time needed to adapt, unlike rival Michael Andretti.
23 KLAUS LUDWIG
There wasn't much Klaus Ludwig didn't win with a roof over his head. In addition to his three triumphs in the Le Mans 24 Hours, he won titles in the DRM, the DTM and the FIA GT Championship. So what's to say he couldn't have succeeded in F1?
The German had a mediocre record over two part seasons in F2, but then that was the first time he'd raced a single-seater.
There was talk, he reveals, of driving for the ATS team in 1977, but the deal never came to fruition. And one of the best German drivers of his generation was lost to F1.
22 FRANK MATICH
When Frank Matich went wheel-to-wheel with some of the world's best drivers in Tasman Series races in the mid-60s many thought the Sydney driver would be the next Australian to take on Europe.
He wasn't - but it was not for lack of opportunity. None other than Colin Chapman offered Matich a drive.
"I was rather surprised that he was quite serious but it just wasn't practical," says Matich today. "I was lucky to have the Total sponsorship going, but they did not have any international racing programmes. So out of respect to them, I said no."
Matich's career hit a snag when he suffered burns at Lakeside in 1965, which meant he had to turn down an offer to test Ford's GT40 in Europe. With a growing family and business commitments, he stayed down under.
Matich went on to race sportscars and Formula 5000s of his own design. In the F5000s, he won five Tasman races and two non-F1 Australian Grands Prix. He retired in 1974.
21 WILL POWER
Like most Australians who make their way to Europe, Power struggled for backing while trying to climb the single-seater ladder.
At one stage, assistance from Mark Webber was needed to keep him going. But even then, results in F3 and Formula Renault 3.5 were far from extraordinary and the prevailing opinion of Power was of a driver with a lot of raw talent, but lacking the ability to refine it.
He opted to switch to the United States, eventually landing his big break with Penske in 2009.
Unsurprisingly, the environment at Penske helped Power unleash his potential and he has been a potent force on road and street courses. Sadly, aside from a single Minardi test at Misano in 2004, he never seriously got on the F1 radar.
20 GERRY BIRRELL
In June 1973, everything seemed set up perfectly for Birrell's racing career. He had impressed in both single-seaters and roofed machinery and Ford had as good as guaranteed his graduation to F1 for the following season.
There's a very good chance this would have been with Tyrrell in place of the retiring Jackie Stewart alongside Francois Cevert had fate not intervened.
Birrell suffered an accident that had some horrifying similarities with the one that would claim Cevert. A tyre is believed to have let go on his Chevron B25 at the ultra-fast Six Freres corner at Rouen-Les-Essarts, pitching him into the barrier. He was killed instantly.
19 SCOTT DIXON
The New Zealander by-passed Europe entirely, moving from his early days in Australian single-seaters across to Indy Lights in 1999. After winning that title in 2000, he stepped up to Champ Car and then IndyCar, winning the 2003 title with Ganassi.
That success brought him to the attention of Williams which, after a promising showing in March 2004 at Paul Ricard, gave him a three-day evaluation test at Barcelona a month later. Sadly, it came to nought.
"At the time, we were mid-tyre war and the cars were particularly tweaky things to drive, so they had a particularly narrow window that they worked in," says then-test team manager Tim Newton. "And they were 900bhp engines so they were not easy things to drive.
"You couldn't just jump in it. Now, you could make yourself closer, but it was a particularly narrow band. I think he was struggling with the power, the brakes and finding that point on the tyres.
"At the time, we had big test teams and were doing high mileages, so the drivers had vast experience. If you bring a guy in for a couple of days, he's just not going to get near them."
18 ADAM CARROLL
The Northern Irish driver has shone in every category he has competed in, including GP2 and A1GP. But despite landing a testing role with Honda, he has never had the chance to race at the top level.
"Adam is a world class driver with a huge natural ability and added to that formidable racecraft, which is partly due to his enormous determination to win," says Mark Gallagher, whose Irish team ran Carroll to the A1GP title.
"Adam is one of those drivers whose absolute focus on winning means he takes things that bit further. I believe that he would have been, and still would be, an extremely competitive F1 driver."
The problem was sponsorship, or the lack thereof. Had Lola been granted an entry for the 2010 season, he was in the running for a seat, money permitting.
"The Lola business model for F1 was predicated on both drivers bringing some funding," says Gallagher, who was closely involved with the Lola project. "Had we got into F1, our intention was definitely to have him as part of our line-up in respect of finding sponsors who might come in.
"He is the kind of driver who could pull off a giant-killing act."
17 EMMANUEL COLLARD
You'd think that Emmanuel Collard was knocking on the F1 door hard given the number of teams he tested for. The Frenchman got his bum in cars for six outfits, but in reality he only had one real chance to cross the threshold.
Collard, by then a factory Porsche driver four years out of F3000, missed out on victory at Le Mans in 1997 courtesy of a fiery oil leak in the 23rd hour. The race was barely finished when F1 team boss Alain Prost called, asking him to be at Magny-Cours the following day to try-out for the F1 team a day later in the wake of Oliver Panis's leg-breaking accident in the Canadian GP.
"I was completely finished after Le Mans and I hadn't driven an F1 car for a year," he recalls. "I was fast, but I had problems with my neck. Prost said I wasn't strong enough."
That was the end of Collard's F1 ambitions, though he did get to do some straightline testing for Arrows in 1998.
Ricardo Divila, who worked with Collard at the Apomatox F3000 squad, describes him as an "absolute natural".
"But the problem with 'Manu' was that he wasn't pushy enough," he says. "He would sit at home waiting for the phone to ring."
During his first year in cars, in FRenault in France, he got the chance to test for Ligier. After a couple of laps the timing people suggested there must be something wrong.
Divila takes up the tale: "There was a speed trap at Estoril [at the fast double-right after Turn 1], and the timing said he was quicker than regulars Rene Arnoux and Olivier Grouillard. They reset it, and he definitely was quicker."
16 AL UNSER JR
'Little Al' was already an Indianapolis 500 winner and a CART Indycar champion when he got the call to test for Williams in 1991.
Whether the American seriously considered switching codes, or Williams was interested in giving him a race chance, isn't clear but Unser left a lasting impression after five days at Estoril aboard the Williams-Renault FW14 that November.
"I remember he had a very shiny race suit and insisted on having a cigarette between every run," recalls long-time Williams engineer David Brown. "And that he brought his wife with him who told filthy jokes to the crew!
"It seemed like he was on a bit of a jolly, but he could drive. There's no doubt he was quick. He left-foot braked, which was new to us, and explains him cooking the brakes."
The story goes that Frank Williams was enthusiastic about Unser's future as an F1 driver, Patrick Head less so.
Unser has claimed the team's technical boss gave him the cold shoulder. "That sounds about right," reckons Brown.
"An American in a shiny suit sitting on a toolbox having a fag wouldn't endear himself to Patrick!"
15 GREG MOORE
Moore, 24, was in his last outing for Forsythe racing in the 1999 Champ Car season, and had a Penske Racing deal for the following year, when he suffered the accident at Fontana that cost him his life. But according to close friend and rival Dario Franchitti, he had caught the eye of some F1 teams.
"There was an interesting situation at Montreal in 1997," says Dario. "We were hanging out together, watching the Canadian Grand Prix. Jackie was interested in me driving for Stewart GP, but he was also interested in having Greg drive for Stewart.
"With us hanging around together so much it was a case of Jackie saying, 'Can you come back later for a chat... but each of you without your mate!'
"There was definitely interest there, and the Ferrari guys loved Greg, too. Jean Todt was a big fan."
14 JAMIE GREEN
The deal was on the table. At a cut-price £600,000 too.
Jamie Green had just beaten Lewis Hamilton and Robert Kubica to the 2004 F3 Euroseries title, and his team - ASM - was stepping up to the new GP2 category. But the ART outfit was unproven at this level and the new Dallara-Renault had been unreliable in testing.
Green's management was worried his reputation would be damaged and there was a works Mercedes DTM contact on offer too. At a stroke the driver Trevor Carlin reckons is better than Lewis Hamilton turned his back on single-seaters.
Ultimately, Nico Rosberg took the GP2 drive that could have been Green's. ART was the first to team to unlock the secrets of the car set-up and Rosberg romped to the title and a Williams F1 drive.
Green hasn't raced a single-seater since.
13 DON PARKER
A late-starter in car racing, Don Parker was a giant of the 500cc Formula 3 movement in the 1950s, winning a trio of British titles, including the 1959 crown in what had become Formula Junior. Among the names who he used to race with, and beat, was a certain Stirling Moss.
"Don was really very fast," says Moss. "He was the benchmark in 500cc F3. He did his own cars and they were always well prepared.
"Don stuck to smaller cars, I think it was his decision to - he was a strong personality. They were specific to drive and he was very light, which was helpful. But some drivers did make the step up.
"I would have thought with his talent and understanding Don would have been good in more powerful cars."
12 DAN WHELDON
In the immediate aftermath of his first Indianapolis 500 success in 2005, Wheldon was linked to BAR-Honda, but the closest he came to an F1 switch was turning down an offer from BMW Sauber. That chance was snapped up by Robert Kubica - who turned it into a race seat when Jacques Villeneuve split mid-2006.
Wheldon instead signed for Chip Ganassi Racing in IndyCar. At the time he said of the BMW-Sauber deal: "I had a good offer but F1 is a cruel world. There are so many variables you can't control."
The sticking point was the deal didn't offer a guaranteed race seat and, following Wheldon's death in an IndyCar crash in 2011, his long-time agent Adrian Sussman explained: "A big part of Dan's success was knowing that everything was taken care of.
"He was so detail-oriented and specific, he wanted everything to be just perfect."
Wheldon's road-course pedigree was poor compared with his oval success (only one of his 16 wins came on them) but karting peer Anthony Davidson says: "Dan had a smooth style that didn't suit American road courses so much.
"He was definitely a driver who drove with his fingertips - but he was exceptionally brave, even as a kid."
11 GIL DE FERRAN
Twenty years ago, you would have bet the farm on Gil de Ferran making it to F1. He had won British F3 in 1992 and then won races in F3000, only for a lack of opportunities in Europe to force him to cross the pond to race for Jim Hall in CART Indycar.
He did get to test F1 machinery, including a Williams, but perhaps the most significant test came for Footwork at Estoril in 1993. This was the famous test that earned Jos Verstappen the cover of AUTOSPORT for his startling times (at that point, it wasn't well-known that he'd had the chance to adapt to F1 machinery with running in a March).
De Ferran, meanwhile, was brisk but smashing his head in the team's truck won't have helped.
Aside from a stint as Honda (nee BAR) sporting director, this was as close as he got to F1.
10 LAURENT AIELLO
Had Aiello taken up the offer to test an F3000 car before his try-out with McLaren at Estoril in 1994, he might be a successful F1 driver rather than a touring car legend.
Aiello was on his way to the French Supertourisme title in his factory Peugeot when the manufacturer got him a test with McLaren. The problem was that he was two years out of F3000. His engineer at Peugeot, Jacky Eeckelaert, lined up an F3000 test at Lurcy-Levis with the Danielson team to try to get his charge in shape.
"I contacted Joseph Le Bris, a friend of mine, and he agreed that Laurent could test his F3000 car for free, but all he had to do was pay for a set of tyres," recalls Eeckelaert. "But Laurent said, 'oh, I shouldn't have to pay', and he didn't do it."
When Aiello got to Estoril, he was unable to hold his head up in the ultra-fast corners at the beginning and end of the lap. In between, he was more than a match for regular McLaren driver Mika Hakkinen in the Peugeot-engined MP4/9.
"In the tight, technical part - sector two - he was actually quicker than Hakkinen," reveals Eeckelaert. "I don't know if there was ever a chance of him racing for McLaren, because we knew they were going to Mercedes engines, but Laurent was really talented. His problem was that he was too laid back."
Why did your single-seater career stall in Formula 3000?
In 1991, with DAMS, the Lola wasn't the best chassis, but I was one of the fastest drivers in one. [Sponsor] Marlboro realised this and continued my deal, and I was fastest all through winter testing in 1992 with Pacific.
But in the first test with my new Reynard, at Le Mans, the steering broke so I went straight across the Dunlop chicane, was launched very high by the kerbs, and the heavy landing damaged the chassis.
They repaired it very quickly, and I don't know what happened - as soon as the season started I had no grip anymore. It was not a good time, quite honestly.
You still got some F1 tests later on?
I first tested the '94 McLaren-Peugeot at Estoril - it was a very special feeling. But it was really difficult for me, because I hadn't driven a single-seater for a few years. I think I did quite well, but the wish for me to drive came from Peugeot rather than from McLaren.
We did the same later with Eddie Jordan, to push a French driver into his team, but I don't think that was in his plan. I did two tests with Jordan, but I didn't want to do any more - because they only ran me for one day each time so I couldn't show what I was capable of.
9 WALTER ROHRL
The driver of the red Ferrari was definitely getting rattled. So said the driver of the black Ferrari, steadily filling the mirrors of the car ahead, as they tore up Germany's most famous 12.8 miles.
Both cars were on official business at the Nurburgring. One was being driven by a Ferrari driver, the other a Porsche tester who was sampling the hardware being ranged against the latest 911.
It was Michael Schumacher and Walter Rohrl. The double World Rally champion had the advantage of knowing the identity of the man behind the wheel of the red Ferrari. Schumacher had no idea who had the temerity to hustle him like this.
A couple of corners from the end of the lap, a mistake from Schumacher allowed Rohrl up the inside. Victory, in this impromptu road race, was his.
Coming off the track, Rohrl nosed his car out of the circuit, driving slowly to cool the thing down. Stopping at the traffic lights, Rohrl's door was opened by an intrigued and irritated Schumacher, doubtless ready to remonstrate with the fool who had raced him.
Suddenly, everything made sense to the seven-time F1 world champion.
8 GARY PAFFETT
Do you think anyone has ever been so close to F1 and still not made it?
A few people must have, just not anyone I can think of! When I won the DTM, the momentum was with me and I joined McLaren as a test driver. The first opportunity was that year when Juan Pablo Montoya left. I'm still quite frustrated that I didn't get the chance then.
I've never had it fully explained to me why that was. There have been opportunities but none of them have ever been really solid with McLaren. Outside of that we had talks with Sauber in 2005. I was definitely going to be driving for Prodrive if that had come off.
What would Prodrive doing F1 have done for your career?
It's hard to say because some people do a good job and quickly move up the grid and into good cars. Some people end up driving for them year after year and I'm sure that's quite frustrating. I've never turned down the chance of an F1 race seat; there have just been a few that haven't worked out.
Do you need to start a grand prix?
No, not really. If I never start a grand prix I won't be too disappointed. I'm happy with what I've got. It would be nice, but I don't need it.
7 PARNELLI JONES
Parnelli Jones was a success in everything he turned his hand to, be it Indycars, Stock cars or Sprint cars, and there is no doubt that the 1963 Indy 500 winner would have excelled in grand prix racing.
Ultimately, he did reach F1 as an unsuccessful team owner from 1974-76, but had he got behind the wheel 15 years earlier, he had the ability to have just as much success as Mario Andretti in grand prix racing.
6 DAVE COYNE
August 1991: in a GJ Motorsport Reynard run on a frayed shoestring, 33-year-old Dave Coyne dominates a British Formula 3000 round at Snetterton, just third time out in the car. One week later he wins again at Thruxton.
In between he's tested for the FIA F3000 round at Brands Hatch, in GJ's newer car normally 'raced' by Giovanna Amati, and topped the times - quicker than Christian Fittipaldi, Alex Zanardi, Damon Hill, Heinz-Harald Frentzen and Allan McNish.
Meanwhile, he's had a call from Jordan, because Bertrand Gachot has just been sent to prison...
Within a week, all is in tatters. Michael Schumacher's mentors at Mercedes have come up with the money for the Jordan drive, Amati has reclaimed her car for Brands, and Coyne is forced to race his old British-series Reynard. A breakage causes an enormous shunt, which damages the chassis, and Coyne's attempt to deny Paul Warwick a posthumous title is doomed.
That was the last roll of the dice for Coyne, who'd been a superstar of Formula Ford 1600 - on and off - throughout the 1980s.
This had been interspersed with cameo F3 one-offs: a blinding drive at Thruxton in Gary Anderson's Anson in 1981; third and fastest lap at Spa's British F3 round in '84 - with a misfire; trouncing the German F3 regulars (including Bernd Schneider and Kris Nissen) at the Osterrichring in '86 before his tyres went off, having outpaced them by five seconds in wet qualifying!
That shouts 'superstar', had his commitment on the track been matched off it. Even in FF1600 days he was a car dealer, and once explained: "I always had a big mortgage. I don't come from a rich family. Even when you're sponsored, you've got to earn money to live. But that's life isn't it? You can't change it."
5 RICK MEARS
You came close to an F1 drive with Brabham in 1980. What happened?
I can't remember how it all came about but I ended up going to England and meeting with [Brabham team boss] Bernie [Ecclestone] and talking with him about putting something together for Long Beach.
Had F1 been on your radar before that?
A little bit, possibly. It was one of those deals where I thought 'well, it'll probably never happen'. I didn't really believe in getting my expectations too high.
So initially the talk was about doing a one-off at Long Beach?
The Long Beach deal fell through politically. They wouldn't let me run, there were licensing problems.
There was also talk of a full-time move. What happened?
We ended up coming to terms on a full-year contract.
What was the reason for deciding not to make the move to F1?
I was doing what I love doing and I didn't have to prove anything to anybody. I was very fortunate to be able to get that out of my system, to be able to drive the car and say, 'yeah, I know I can do this if I want to' so I satisfied my own ego and my own curiosity because I was only a second or half a second off Nelson [Piquet] at Paul Ricard and I was quicker than him at Riverside [when we tested].
The money was good compared to Indycar but I enjoyed the Penske organisation, we were already family. I didn't necessarily want to do that - and the other thing I enjoyed was [the mix of] ovals and road courses.
4 AJ FOYT
Anthony Joseph Foyt Jr had no time for Formula 1, and did little to hide his disdain for it. He is, however, undoubtedly America's top homegrown single-seater star.
He won a record 159 US open-wheel races - 67 of which were at Champ Car (now IndyCar) level, and won the domestic premier open-wheel series seven times. For an obvious benchmark, he had a huge rivalry with Mario Andretti, who would go on to become Formula 1 world champion while Foyt opted to stay firmly rooted on his side of the pond. But on the rare occasions Foyt did race in Europe, his success rate did not diminish.
He won the 1967 Le Mans 24 Hours, sharing a Ford GT40 MkIV with fellow all-American hero Dan Gurney, and explains: "I went over there as a rookie and won, so I never went back!"
Foyt first raced on European shores back in '58, in the second 'Race of Two Worlds', where he acted as relief driver to F1 racer Maurice Trintignant - "It was fun to drive on the banking at Monza" - but he had to wait until USAC visited the UK in the late '70s to score a single-seater victory, at Silverstone.
"I was chasing [Roger] Penske's cars pretty hard all day," he recounts. "Jackie Stewart told me there was one corner [Stowe] that you can get into a lot harder than you think. I was catching [Rick] Mears and thought, 'I've only got one shot at this - I hope that guy didn't lie!'
"I was on the grass, but we won. Jackie gave me that tip right there."
Stewart (and others such as Jim Clark) held Foyt's talents in high regard, but the majority of F1 did not. And that suited AJ just fine.
3 DARIO FRANCHITTI
Formula 1 was Franchitti's "dream" but despite a trio of half-chances, he would never commit to taking the plunge for a variety of reasons, as he explains...
"At the end of '95, I tested for McLaren. It was my prize for the McLaren AUTOSPORT BRDC Award. We went down to Jerez. I got half a day and [Bernd] Schneider got half a day too.
"I remember it was David Coulthard's first run for McLaren, and my abiding memory is the look on his face after getting out, comparing it with the amazing Williams he'd raced previously!
"That test went pretty well and two years later - after I'd already committed to CART in America - McLaren called with the offer of becoming its F1 test driver. I'd have tested during the week, and flown back and forth to race in America. At the time, I just didn't see it working. So, much to Norbert [Haug]'s amazement - and probably Ron [Dennis]'s too - I said no.
"DC and Mika [Hakkinen] had just signed long-term deals with the team, so I didn't do it. That was my big decision - but I've still got the contract at home, it's about 65 pages long!
"A few years later the guys at BAR came calling. Craig Pollock phoned me and asked if I'd do that. I'd just signed a new deal with Barry [Green, his CART team boss] and I wasn't prepared to run in the midfield or at the back. By then I would have had to give up a lot in America for a half chance in F1.
"It's a stark contrast to Paul [di Resta]'s approach - he gambled it all on making it in F1, and I'm so proud of him achieving that. I was never prepared to do that; I'd built my life in the States.
"The Jaguar test [at Silverstone in 2000] came about after a chat with Jackie [Stewart]. It turned out to be a farce from start to finish; it's the only way to describe it! After the first day the car swapped, and I don't know if I was running older-spec parts or what.
"Even recalling how much that Jag sucked, it still didn't put me in a very favourable light at all. It was a pretty dreadful few days.
"Something I guess not a lot of people know is that I was still recovering from a shunt at Homestead at the start of the season. I had ruptured discs in my neck, which made it pretty difficult to jump into an F1 car! It was a combination of things, and I don't think the team particularly wanted me in there.
"There was a race contract in place before I even sat in the car, but I got a call two days later from Neil Ressler saying, 'Nah, we don't want to do this', to which I replied: 'Good, neither do I!' And that was the end of that."
Q&A BOBBY RAHAL
Former Jaguar team boss
What's your view on Dario Franchitti's Jaguar test?
I wasn't at Jaguar when Dario did his test. But by all accounts I don't think he got a fair shake. Again, that was before my time, but it's a shame, because I think Dario could have succeeded in F1.
Why wasn't he given a fair chance?
I don't know. Of course there are all kinds of rumours and what-have-you that there was never any kind of real interest; that it was kind of being foisted upon Jaguar by Ford. Even though Ford owned the company, it was still being run by the ex-Stewart guys. So the rumours were that there was never any real support and that they just went through the motions. And by all accounts, it was a problematic test.
And of course, in F1, if you don't light the world up in your first test then you're nobody. But from everything I've heard, it wasn't a fair test. And I think there were all kinds of car problems; all kinds of issues, and I think all of that conspired against Dario.
2 SEBASTIEN LOEB
In the words of Sebastien Loeb himself, "it came close, very close, to happening. But in the end, there was this thing with the superlicence and so that was that. It just wasn't meant to be."
The "it" to which the nine-time World Rally champion is referring was the chance to compete in the 2009 Abu Dhabi Grand Prix with Toro Rosso, which may or may not have led to a race drive in 2010.
The groundwork began in '08, the year Loeb's Citroen team first carried Red Bull sponsorship in the WRC, which coincided with when the energy drink went on sale in France after being prohibited for many years.
This led to a personal Red Bull deal with Loeb and a Formula 1 test with Red Bull Racing at Silverstone privately, and then at Barcelona for the official test in November a week later.
You can obviously make statistics up out of anything you like, but the fact is that Loeb's 1m22.503s would still have put him 16th on the grid for this season's race at Barcelona, five years later. And at the time he felt that he had a good second still left in him. It was only one day of testing after all.
So it all suddenly got a lot more serious, with Loeb embarking on an F1 fitness programme at the age of 34 and also taking part in GP2 testing.
"The idea of driving a Formula 1 car just started off as a bit of fun through Red Bull," he points out. "But it was one of those things that somehow became more substantial as time went on. I wasn't talking about this with so many people but already back then I was thinking of perhaps doing something else.
"So from being just a publicity stunt in the beginning, that test maybe turned into a career opportunity that seemed quite exciting for a while. I don't know. I was ready to do Abu Dhabi, but I have no idea what would have come of it afterwards. Probably nothing."
Any regrets? "No, not at all. I don't think F1 is something you can just jump into and be instantly competitive."
Then a pause, and a wry half-smile that is typically Loeb. "But it would have been nice..."
1 TOM KRISTENSEN
TK did everything but race in F1 before establishing himself as a sportscar superstar. A champion in German and Japanese F3 and a race-winner in F3000, he also tested for Minardi (pictured), Tyrrell and Williams.
Notably, he impressed Michelin hugely with his tyre testing using Williams machinery, even though to the outside world his times were unremarkable.
"The first time that a Williams-BMW left the garage was at the end of 1999 with Tom at Jerez," says then-Williams test-team manager Tim Newton.
"We were finding quite a lot of problems and had quite a challenging winter. We were pretty unreliable in the first few tests.
"Tom did a very good job, not right at the top super-fast, but lots and lots of very consistent laps, which is what you need. The engineers have a programme to get through, and it's not qualifying. If it was, you could make a driver look great, but if the emphasis is on how long the tyres last, or how consistent it is, it's a different type of driving."
Ultimately, driving ability alone wasn't enough to haul Kristensen into F1. As manager Werner Heinz admits: "If I had the experience I have today [of negotiating] then Tom would have been in at Williams. Michelin wanted him."
Does it bother you that racing in F1 is not on your CV?
I love motorsport. I'm privileged in what I've been able to achieve. Being from a small country like Denmark has always meant that F1 is too far, realistically, for any Dane. That was always imprinted on me, even though I was born on a gas station.
I have been very fortunate to be able to make it to being a professional. It was my dream, but not a realistic dream until I realised I was beating drivers that had made it there themselves. Then I worked hard at it. Since I won Le Mans the first time, I joined BMW with the intention of getting to F1 with Williams. That's the closest I got.
I'm very happy with the decision I made to join Audi at the end of '99 though. I don't regret it for a second.
How close were you to a Prost seat - Alain tells AUTOSPORT that he wanted you for 2000?
It's hard to say because there was a financial element there. I've always been weak in that area and never really had that level of financial support. The people I know had contact with Prost Grand Prix at the time and it was interesting. It's kind of him to mention it now.
Then again, you might have driven an uncompetitive Prost so never had that success with Audi?
It's true. I told you I don't regret joining Audi.
Michelin was keen on you for F1 thanks to your tyre-testing performances...
I needed to take the tyre testing very seriously and giving them good feedback helped me. But they gave me the mileage too. Doing that was important, but when I did that in 2000 I was already with Audi.