Former champion Jack Kennedy led the way in the wet at Knockhill this morning, as he stormed to the best lap of the session.
Clocking a 54.024sec lap on his penultimate run, the Honda Racing UK rider beat Rhys Irwin by 0.201secs.
Irwin, now riding the Gearlink Kawasaki after a late switch of team, managed to hold off Luke Stapleford to end his first session on his new machine in a comfortable second.
Luke Jones ended the session fourth, with Alastair Seeley fifth.
In GP2, Jack Nixon looked to have found the form demonstrated earlier in the year as he led the class, finishing seventh overall. Kramer Racing team-mate Owen Jenner was second, with Keo Walker third.
Lynden Leatherland was quickest in the Cup, with Mikey Hardie second and Adon Davie third.
Quattro Group British Supersport and GP2/HEL Supersport Cup, Free Practice 1:
1. Jack Kennedy (Honda Racing UK)
2. Rhys Irwin (Gearlink Kawasaki) +0.201s
3. Luke Stapleford (Macadam Triumph Racing) +0.272s
4. Luke Jones (Highsparks Ducati) +0.303s
5. Alastair Seeley (Binch Pro Yamaha) +0.504s