Ben Currie held off Luke Stapleford to lead the opening Supersport session with a best lap of 1min 39.349secs.
The Oxford Products Racing Ducati rider beat his Profile Road & Racing Performance rival by 0.108secs as Tom Toparis was third quickest ahead of Zak Corderoy and Richard Cooper on the Russell Racing Yamaha.
In GP2, Joe Collier took charge, ending the session ninth overall as Cameron Fraser was second and Harry Rowlings third.
Quattro Group British Supersport & British GP2 Championships, FP1:
1. Ben Currie (Oxford Products Racing Ducati) 1min 39.349s
2. Luke Stapleford (Profile Road & Racing Performance) +0.108s
3. Tom Toparis (Macadam Racing) +0.150s
4. Zak Corderoy (Gearlink Kawasaki) +0.270s
5. Richard Cooper (Russell Racing) +0.299s