Jack Kennedy powered straight to the top of the timesheets to lead the opening session with a hot lap of 1m:08.883secs over Bradley Perie.
Zak Corderoy was a close third, just ahead of team-mate Zac Corderoy while Harry Truelove ended the session fifth.
In the GP2 class, Jack Scott looked untouchable, ending the session sixth overall and more than 1.5s clear of Cameron Fraser with Harvey Claridge third.
Quattro Group British Supersport, Free Practice One:
1. Jack Kennedy, Mar-Train Racing
2. Bradley Perie, Appleyard Macadam Racing +0.394s
3. Zac Corderoy, Gearlink Kawasaki +0.739s
4. Luke Stapleford, Gearlink Kawasaki +0.959s
5. Harry Truelove, Appleyard Macadam Racing +1.033s