Alastair Seeley drew first blood as the Pirelli National Superstock machines powered into action, beating points leader Dan Linfoot to the top spot.
Seeley clocked a 1min 36.562sec lap to go 0.268secs clear of his rival, as Ash Beech rounded out the top three.
Alex Olsen, returning from injury on the Cumins by Team IWR Honda, managed to get himself up to fourth place, just ahead of Scotland’s Lewis Rollo in fifth.
Pirelli National Superstock with Santander Consumer Finance, FP1 result:
1. Alastair Seeley (SYNETIQ BMW Motorrad) 1min 36.562s
2. Dan Linfoot (Optimum Bikes Racing Ltd) +0.268s
3. Ash Beech (Jones Dorling Racing) +0.338s
4. Alex Olsen (Cumins by Team IWR Honda) +0.478s
5. Lewis Rollo (IN Competition/Aprilia) +0.481s