Glenn Irwin pipped title challenger Alastair Seeley in a Carrickfergus one-two in Saturday's British Superpsort sprint race at Brands Hatch.
Irwin beat Seeley by 0.2 seconds for his fifth win of the season while Luke Jones completed the podium.
Seeley trails leader Billy McConnell by 21 points going into Sunday afternoon's final race of the season.
Irwin, who has won the last two races in the championship, is fourth in the series and out of title contention.
Seeley is six points behind second-placed Graeme Gowland going into the title decider on Sunday.
Jordanstown rider Andy Reid will be involved in a 'winner-takes-all' shootout for the British Superstock 600cc title at the English circuit.
The 20-year-old FFX Yamaha rider trails series leader Joe Collier by four points and second-placed Kyle Ryde by three points.