Zak Corderoy ended the opening day at Cadwell Park at the top of the timesheets after banking the fastest free practice lap just moments before the track was hit by rain.
Corderoy clocked a 1min 29.065s lap with just over seven minutes of the session to run – and it was to be a time that stuck as rain returned two minutes later, preventing anyone from going faster.
Early session leader and title challenger Rhys Irwin ended the day second quickest, 0.377secs adrift as FP1 leader Ben Currie managed to hold onto third thanks to his morning lap time.
Tom Toparis was fourth, setting his best lap in the second session as Luke Stapleford held onto fifth with his lap from the previous session.
Joe Collier continued to nip at the heels of the main runners as he set the eighth best lap overall on the Kramer to head the GP2 class, with Cameron Fraser second and Luca Allen third.
Quattro Group British Supersport & British GP2 Championships, Combined classification:
1. Zak Corderoy (Gearlink Kawasaki) 1min 29.065s
2. Rhys Irwin (Astro-JJR Suzuki) +0.377s
3. Ben Currie (Oxford Products Racing Ducati) +0.519s
4. Tom Toparis (Macadam Racing) +0.729s
5. Luke Stapleford (Profile Road & Racing Performance) +0.915s