Championship leader Edoardo Colombi saw off a charging Richard Cooper to top the timesheets at the end of day one at Donington Park, with a best lap of 1min 36.231s.
The Italian was almost half a second quicker than Cooper, as Ash Barnes ended the day a close third.
Harrison Dessoy was fourth quickest on combined times, with Aaron Silvester fifth.
Pirelli National Sportbike with Moneybarn Vehicle Finance, combined practice:
1. Edoardo Colombi (Gradara Corse Asd) 1min 36.231s
2. Richard Cooper (PHR Performance Triumph) + 0.467s
3. Ash Barnes (Raceways Yamaha) +0.618s
4. Harrison Dessoy (Rev2Race Yamaha) +0.774s
5. Aaron Silvester (MH Solutions/Macadam Racing) +0.848s