It was Tom Sykes who took the lead in to Coppice on the opening lap onboard the Rizla Suzuki, with the HM Plant Honda duo Cal Crutchlow and Leon Haslam flying in second and third.
However Crutchlow crashed out on the third lap as the pack streamed in to Hall Bends.
Haslam was then in second and closing down the leading Rizla Suzuki rider, he then dived down the inside at Park on lap six to take the lead.
Haslam and Rizla Suzuki's Tom Sykes were then inseparable as the pair diced at the front, with Sykes looking for any opportunity to take back the advantage - but it was not enough and he had to settle for second.
* Louth rider Peter Hickman rode to his first podium finish of the season when he took a fine third place in round nine of the Metzeler National Superstock championship at Cadwell on Monday to move up a place in the rider points to six place with three rounds left to race.
"Its been a fantastic weekend," Said Hicky. "It's been a long time coming but here we finally are on the podium."
The next round is at Croft in North Yorkshire on September 14 but before that Hicky is to ride at Donington Park in the European Superstock championship where he has been awarded a wild card ride on September 7.
* There was drama at the Cadwell Park campsite on Sunday afternoon when an unattended barbeque started a fire which torched seven tents and damaged a Vauxhall Astra and a caravan.
The British Supersport final qualifying session had to be stopped because smoke was billowing across the track. A fire crew from the circuit was despatched to put out the fire.