Richard Cooper stole the top spot from points leader Ben Currie in the closing moments of second practice to end day one on top.
With no BMW action this weekend, Cooper is back in Supersport action on the BPE Yamaha and clocked the best lap of the day with a 1min 37.990s to knock Currie down to second just as the flag fell.
Cooper’s lap was 0.337secs quicker than Currie, who had moved to the top of the timesheets just two minutes earlier deposing Eunan McGlinchy, who ended the session third.
Jamie Perrin and his Astro JJR Suzuki team-mate Rhys Irwin finished fourth and fifth respectively at the end of the session, which was red-flagged twice due to crashes on track.
Cameron Fraser remained on top in the GP2 battle, with Harvey Claridge second and Harry Rowlings third.
Quattro Group British Supersport & British GP2 Championships, FP2 result:
1. Richard Cooper (BPE Yamaha) 1min 37.990s
2. Ben Currie (Oxford Products Racing Ducati) +0.337s
3. Eunan McGlinchey (Eunan McGlinchey Racing) +0.338s
4. Jamie Perrin (Astro-JJR Suzuki) +0.524s
5. Rhys Irwin (Astro-JJR Suzuki) +0.627s