Dunlop crossed the line in 14th place on the Buildbase Suzuki on his return to the class, with the Ballymoney man filling in for the injured Danny Kent.
The 19-time Isle of Man TT winner has close ties with Stuart and Steve Hicken’s Hawk Racing outfit, winning the Senior TT on the Bennetts Suzuki in 2017, and clinching a Superbike and Senior double on BMW machinery in 2016.
Fellow road racing star Dean Harrison was 12th on the Silicone Engineering Racing Kawasaki, while Peter Hickman – who is challenging for the title in the Showdown – was fifth on the FHO Racing BMW.
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Race two at Oulton was won by Tommy Bridewell on the Oxford Products Racing Ducati by 0.4s from Showdown leader Jason O’Halloran (McAMS Yamaha), with Tarran Mackenzie a close third on the second of the McAMS Yamaha machines.
Andrew Irwin was ninth on the SYNETIQ BMW although there was disappointment for his brother and Showdown contender Glenn, who crashed out on the Honda Racing Fireblade after starting from pit lane.