Sullivan Mounsey held off a charging Harley McCabe to take the opening R&G British Talent Cup win of the weekend.
The Wilson Racing/Maddison Media rider hit the front on the opening lap and managed to hold it to the flag to celebrate his second win of the year.
Alexander Rowan beat Lucas Brown to third place in a last lap drag to the line as Ollie Walker took fifth.
Points leader and polesitter Evan Belford had been running in fourth position but crashed out on the penultimate lap.
R&G British Talent Cup, Race One result:
1. Sullivan Mounsey (Wilson Racing/Maddison Media)
2. Harley McCabe (McCabe Racing) +0.187s
3. Alexander Rowan (Mortimer Racing Victoria House Academy) +8.021s
4. Lucas Brown (Amphibian Scaffolding/SP125 Racing) +8.090s
5. Ollie Walker (VisionTrack Racing Team) +32.578s