Mikey Hardie beat James McManus to take the opening Junior Supersport win by 0.150secs.
After a strong start to the weekend, Hardie held off a charging McManus over the line as Joe Ellis took third. Calum Beach was fourth, as Abbz Thomas took fifth.
HEL Performance British Junior Supersport Championship with Motocourse, Donington Park, Race One:
1. Mikey Hardie (Completely Motorbikes/Affinity)
2. James McManus (Completely Motorbikes/Affinity) +0.150s
3. Joe Ellis (JPR) +0.150s
4. Calum Beach (UPVC Outlet Racing) +3.354s
5. Abbz Thomas (Symcirrus Motorsport) +3.526s