Rene Rast took the lead of the Porsche Mobil 1 Supercup standings with a third victory of the season at Silverstone.
The double champion had posted the fastest time in qualifying but had that taken away from him for exceeding track limits. He put that behind him to get ahead of poleman Kuba Giermaziak at the start and take the lead.
A poor getaway quickly saw Giermaziak shuffled back to fourth, behind Sean Edwards and Norbert Sieler.
British driver Edwards was chasing a second home victory, but Rast was too strong and held on to the lead.
“That was a perfect race,” said Rast. “Despite making a clean start and putting some space between me and my pursuers, I knew right from the start that it wouldn't be easy.
“Unlike my rivals I didn't have any new tyres at my disposal, and especially here in Silverstone that can make all the difference. And I noticed this. Sean was able to drive a much tighter line, he could brake later and hit the throttle earlier. I had to defend my position, so I tried out different lines and I'm pleased that it was enough to get me to the flag first.”
Second-place would have been enough for Edwards to retain the championship lead, but Siedler did his Lechner Racing teammate Rast a favour by getting past for second place on the penultimate lap.
“From fifth on the grid to second at the flag, I'm happy with that,” said the Austrian. “I think I might have surprised Sean with my overtaking manoeuvre shortly before the finish. The points I earned are crucial towards the championship. Now we're focussing on Hockenheim where it'll be 'max attack'.”
Edwards added: “I was quite fast early on with fresh tyres and could catch RenÃ©. With an eye on the championship I wasn't prepared to risk too much so I settled in behind him. Actually, there wasn't really a chance to overtake anyway. Norbert's move just before the flag took me by surprise. In fact, I almost lost control of my car.”
That manoeuvre by Siedler put the top three within two points of each other in the championship. Rast leads on 78, with Edwards and Siedler both on 77. Rast had taken the lead with a Silverstone win 12 months ago, going on to win the crown.
Giermaziak finished fourth, ahead of his fellow Pole and teammate at VERVA Racing Team Patryk Szczerbinski, who claimed his best Supercup finish of fifth.
Kevin Estre was sixth, ahead of rookies Michael Ammermuller and Nicki Thiim.