Richard Kerr held off Dan Linfoot to take the National Superstock win after a race-long battle where the lead changed many times between several riders.
Linfoot had led into the final lap but had Kerr snapping at his heels, the lead swapping between the pair twice before Linfoot made a move into the loop but ran wide, allowing Kerr to take the place back and cross the line as winner.
Earlier leader Alastair Seeley had to settle for third, just ahead of Joe Talbot as Lewis Rollo took fifth.
Pirelli National Superstock with Santander Consumer Finance, Race result:
1. Richard Kerr (AMD Motorsport)
2. Dan Linfoot (Optimum Bikes Racing Ltd) +0.393s
3. Alastair Seeley (SYNETIQ BMW) +1.192s
4. Joe Talbot (JR Performance Racing) +4.382s
5. Lewis Rollo (IN Competition/Aprilia +6.978s
Championship points after Round Four:
1. Dan Linfoot 87
2. Richard Kerr 79
3. Joe Talbot 68
4. Franco Bourne 67
5. Alex Olsen 59