Outgoing champ Ben Currie set the pace as the Supersport action fired up this morning, banking a best lap of 1min 29.585secs.
The Oxford Products Racing Ducati rider saw off a charging Stapleford who finished the session second and just 0.029secs adrift, as points leader Jack Kennedy was third.
Fourth quickest was Shane Richardson with Eugene McManus fifth.
Cameron Hall led the Cup class, ending top in class and 15th overall while Owen Jenner led the GP2 class, finishing 16th.
Second in the cup was Adon Davie with Tom Tunstall third, while Jack Nixon was second in GP2, with Keo Walker third.
Quattro Group British Supersport& GP2/HEL Supersport Cup, Free Practice One:
1. Ben Curie (Oxford Products Racing Ducati) 1min 29.585s
2. Luke Stapleford (Macadam Triumph Racing) +0.029s
3. Jack Kennedy (Honda Racing UK) +0.466s
4. Shane Richardson (Astro-JJR Hippo Suzuki) +0.763s
5. Eugene McManus (ROKiT Haslam Racing Ducati) +0.880s