Reigning British Touring Car champion Andrew Jordan won the reversed-grid race at Croft after a chaotic encounter.
The race had four leaders in the first half lap. Poleman Jack Goff led initially, but clashed with Tom Ingram's Speedworks Toyota between the first and second corners.
Goff went off and Ingram did likewise at the chicane, allowing Fabrizio Giovanardi's Motorbase Ford Focus into the lead.
The former double champion made it as far as Barcroft before a touch from Jordan helped the Ford into the barriers.
"I think he had a problem with his car, because of the closing speed at the Jim Clark Esses" said Jordan of the clash.
Jordan thus moved to the front, while the safety car was scrambled.
After the restart, Matt Neal - having already hit the Toyota of Glynn Geddie as the Honda charged from the back - went three-wide with Rob Austin's Audi and the BMR Vauxhall of Warren Scott.
The result was all three going off the road and an unimpressed Neal soon toured into the pits to retire.
Following him into retirement was double Croft winner Colin Turkington, who had been running sixth, with suspected clutch failure.
While Jordan drove off to win, Goff found himself under attack from Rob Collard's WSR BMW in the battle for second.
That was resolved when Collard hit Goff at Sunny Out, a move that also allowed Mat Jackson's Motorbase Ford to pass the Insignia.
Gordon Shedden's Honda Civic Tourer, which had started from row four, was the next to challenge Goff. He overtook the Vauxhall with a robust move at Sunny and soon attacked Jackson.
On the penultimate lap, Shedden made it by the Ford at Hawthorn to secure his third podium of the day, as he pulled clear of Jackson.
Goff's bruising race continued right until the last corner where he ran wide. That allowed Adam Morgan's Ciceley Mercedes to get the better exit and beat the Vauxhall to the line by a nose to finish fifth.
The Triple Eight MGs continued to struggle, title contender Jason Plato only making it as high as 10th after his grid penalty for contact with Alain Menu in race two.
Results - 18 laps: Pos Driver Team/Car Time/Gap 1. Andrew Jordan Eurotech Honda 28m24.822s 2. Rob Collard WSR BMW +3.492s 3. Gordon Shedden Honda +14.940s 4. Mat Jackson Motorbase Ford +18.517s 5. Adam Morgan Ciceley Mercedes +19.179s 6. Jack Goff BMR Vauxhall +19.180s 7. Nick Foster WSR BMW +19.382s 8. Alain Menu BMR VW +19.751s 9. Aron Smith BMR VW +20.397s 10. Jason Plato MG +21.370s 11. Martin Depper Eurotech Honda +29.252s 12. Hunter Abbott RAR Audi +29.334s 13. Sam Tordoff MG +32.097s 14. Lea Wood Houseman Toyota +33.467s 15. James Cole UA Toyota +34.295s 16. Dave Newsham AmD Ford +38.948s 17. Warren Scott BMR Vauxhall +46.649s 18. Simon Belcher Handy Toyota +50.523s 19. Ollie Jackson Welch Proton +50.475s 20. Aiden Moffat Moffat Chevrolet +1m19.750s Retirements: Jack Clarke Motorbase Ford 10 laps Glynn Geddie UA Toyota 9 laps Marc Hynes MG 8 laps Dan Welch Welch Proton 8 laps Colin Turkington WSR BMW 7 laps Matt Neal Honda 6 laps Rob Austin RAR Audi 5 laps Fabrizio Giovanardi Motorbase Ford 5 laps Robb Holland Rotek Audi 4 laps Tom Ingram Speedworks Toyota 0 laps