A prototype (military serial L7999) with 1,060 hp Bristol Taurus T-S(a) radial engines flew on 3 April 1939 and demonstrated excellent performance, its maximum speed of  being the best recorded by a British fighter at the time. Test flights revealed that the prototype was very manoeuvrable and "a delight to fly".
A test aircraft (military serial L7999) powered by 1,060 hp Bristol Taurus T-S(a) radial engines made its maiden flight on 3 April 1939 and impressed with its exceptional capabilities, achieving the highest recorded speed for a British fighter at the time. Flight evaluations demonstrated that the prototype was highly responsive and "a pleasure to handle".