Charlie Barnes took FP1 bragging rights after topping the timesheets after a damp session with a best lap of 1min 48.951secs.
The SENCAT Talent Team/Mortimer Racing rider beat team-mate Lucas Brown by 0.455secs, as Harley McCabe rounded out the top three.
Alexander Rowan banked the fourth best lap, with Daniel Goodman fifth.
R&G British Talent Cup, FP1:
1. Charlie Barnes (SENCAT Talent Team/Mortimer Racing) 1min 48.951s
2. Lucas Brown (SENCAT Talent Team/Mortimer Racing) + 0.455s
3. Harley McCabe (Fibre Tec Honda) +1.059s
4. Alexander Rowan (Alexander Rowan Racing) +1.493s
5. Daniel Goodman (Fibre Tec Honda) +1.557s