Luke Mossey laid down the best time of the opening session at Donington Park to go almost a second faster Davey Todd.
The Milenco by Padgetts Motorcycles rider banked a lap of 1min 31.575secs, 0.950s quicker than Todd, as David Allingham was third.
Todd’s main title rival Joe Talbot was fourth, with Josh Owens fifth.
Pirelli National Superstock with Moneybarn Vehicle Finance, FP1:
1. Luke Mossey (Milenco by Padgetts Motorcycles) 1min 31.575s
2. Davey Todd (Cheshire Mouldings BMW by TAS Racing) +0.950s
3. David Allingham (SMS/Nicholls Oil Racing) +1.624s
4. Joe Talbot (SAF INTRADISC Honda by JR Performance) +2.125s
5. Josh Owens (IN Competition/SENCAT Aprilia) +3.019s