Samsung Crescent Suzuki rider John Hopkins has won the first race of the showdown at Donington Park in his first race back from injury.
Swan Yamaha's Michael Laverty was quickest off the line, with Byrne close behind and the two trading places in the early stages of the race.
HM Plant Honda's Shane Byrne was leading the race ahead of Tommy Hill on lap 12 when Hill made his move. Hill out-braked Byrne into the final corner but ran wide, also pushing Byrne wide.
This allowed both Laverty and Hopkins to go through to first and second. From there they slowly pulled away from Hill and Byrne, with Hopkins patiently stalking the Swan Yamaha rider.
Hopkins made his move in to the esses on lap 17 and then pulled away easily to take the win.
Title hopefuls Josh Brookes and Ryuichi Kiyonari both struggled, with Brookes finishing in sixth. Kiyonari was circulating with Brookes but a technical problem forced him to retire on lap 12.
Tommy Hill leads the championship on 545 points, with Hopkins close behind on 543.
Tommy Hill 545
John Hopkins 543
Shane Byrne 535
Michael Laverty 530
Josh Brookes 519
Ryuichi Kiyonari 508