Jack Dunabie signalled his intentions for the weekend ahead by beating championship leader Ryan Frost to the FP1 top spot by 0.055secs.
Dunabie, who trails Frost by 26 points coming into this final weekend for the series with three races, clocked a 1min 39.024sec lap to draw first blood ahead of his rival.
Luke Fitchett was third quickest with Marco Holt fourth and Mason Foster fifth.
R&G Moto4 British Cup, FP1:
1. Jack Dunabie (Kovara Projects/RS Racing) 1min 39.024s
2. Ryan Frost (Fibre Tec Honda by MLav Racing) +0.055s
3. Luke Fitchett (Kovara Projects/RS Racing) +0.548s
4. Marco Holt (City Lifting/RS Racing) +0.759s
5. Mason Foster (Ultra Whippet) +0.763s