Tom Booth-Amos banked maximum points after beating Rhys Irwin to the Sprint race win – as polesitter Luke Stapleford crashed on the penultimate lap.
With a comfortable lead, Stapleford made a tiny mistake on lap nine of 10 to crash out, losing his points lead as Booth-Amos came through and took the win.
Irwin, who had led for the first three laps before being passed by both Stapleford and then Booth-Amos, eventually took second, 2.282secs behind the winner.
Ben Currie was third as Jaimie van Sikkelerus was fourth with Luke Jones fifth.
In GP2, it was Joe Collier on the Kramer who took the class win, with Cameron Fraser second and Harvey Claridge third.
Quattro Group British Supersport & British GP2 Championships, Sprint race result:
1. Tom Booth-Amos (Gearlink Kawasaki)
2. Rhys Irwin (Astro-JJR Suzuki) +2.282s
3. Ben Currie (Oxford Products Racing Ducati) +4.198s
4. Jaime van Sikkelerus (MPM Routz Racing Team) +5.696s
5. Luke Jones (Highsparks Ducati) +8.458s