Jake Hill took a controversial first British Touring Car Championship win after making contact with Matt Neal in the Oulton Park finale.
The Audi S3 driver was drawn on pole for the partially-reversed race three grid but was forced to defend from Neal immediately as the Team Dynamics driver made the superior getaway.
As Hill closed off the attack, it compromised Neal's line and so he then had to turn his attention to third-starting Jason Plato.
But Neal maintained the place as Hill edged ahead by three tenths at the end of the opening lap.
The three-time champion aborted a couple of lunges on Hill, but then out dragged the Audi S3 across the line.
Neal momentarily had first place at the apex of the first corner but as he moved his Honda Civic Type R across the track and back onto the racing line, Hill appeared to nudge the back of his car.
That sent Neal into a spin and tumbling down the order, with Plato and Tom Ingram also caught up in the incident.
Plato was able to rejoin, but the damage to his Vauxhall Astra caused it to lay down a film of oil on the way to Island Bend, which sent several drivers spearing off on to the grass.
Up front, Hill was left with a 5.982 second lead over Rory Butcher, who had moved up from fifth on the grid in the melee.
Butcher banged in a run of fastest laps to tear at Hill's lead - going up to 0.9s faster than Hill on each tour - and he dragged himself to the back of the Audi.
It looked set for the two AmD Tuning cars to battle it out for the win, but Butcher was caught out on the oil on the run into the hairpin as he closed to Hill's bumper.
He out braked himself and ran straight on and across the grass, which dropped him down to sixth place.
That left Hill to run home almost a second clear of Stephen Jelley in the BMW 125i M Sport.
Tom Oliphant was the highest placed WSR driver, taking his second BTCC podium this season in the 330i M Sport with third.
Butcher's team-mate Sam Tordoff climbed to fourth amid the drama, while Andrew Jordan rounded out the top five.
Behind the recovering Butcher, Josh Cook scored seventh place as Ashley Sutton and race one and two winner Colin Turkington scrapped for eighth and ninth.
It was Sutton who claimed eighth, as Turkington's nudge on Cook through Druids forced the BMW driver off line and Sutton moved by.
Aidan Moffat closed out the top 10 ahead of fellow Mercedes A-Class driver Adam Morgan and the infuriated Neal.
Result - 15 laps
|1||Stephen Jelley||Team Parker Racing||BMW||22m10.056s|
|3||Sam Tordoff||AmD Tuning||Honda||2.709s|
|5||Rory Butcher||AmD Tuning||Honda||4.510s|
|6||Josh Cook||BTC Racing||Honda||5.973s|
|7||Ash Sutton||BMR Racing||Subaru||6.271s|
|9||Aiden Moffat||Laser Tools Racing||Mercedes||11.323s|
|10||Adam Morgan||Ciceley Motorsport||Mercedes||12.719s|
|11||Matt Neal||Team Dynamics||Honda||16.536s|
|12||Tom Chilton||Motorbase Performance||Ford||16.770s|
|13||Ollie Jackson||Motorbase Performance||Ford||18.331s|
|14||Jake Hill||Trade Price Cars Racing||Audi||19.049s|
|15||Carl Boardley||Team Hard||Volkswagen||22.258s|
|16||Daniel Rowbottom||Ciceley Motorsport||Mercedes||22.991s|
|17||Dan Cammish||Team Dynamics||Honda||23.643s|
|18||Mark Blundell||Trade Price Cars Racing||Audi||26.134s|
|19||Nicolas Hamilton||Motorbase Performance||Ford||27.920s|
|20||Senna Proctor||BMR Racing||Subaru||28.393s|
|21||Sam Osborne||Excelr8 Motorsport||MG||34.542s|
|22||Michael Crees||Team Hard||Volkswagen||37.748s|
|23||Rob Collard||Power Maxed Racing||Vauxhall||37.854s|
|-||Matt Simpson||Simpson Racing||Honda||Retirement|
|-||Bobby Thompson||Team Hard||Volkswagen||Retirement|
|-||Tom Ingram||Speedworks Motorsport||Toyota||Retirement|
|-||Chris Smiley||BTC Racing||Honda||Retirement|
|-||Jason Plato||Power Maxed Racing||Vauxhall||Retirement|
|-||Jack Goff||Team Hard||Volkswagen||Not started|
|-||Rob Smith||Excelr8 Motorsport||MG||Not started|