 The F.9/37 was designed under the direction of George Carter, his first for Gloster, to F.9/37 (hence the name) as a single-seat fighter carrying an armament of four 0.303 in (7.7 mm) Browning machine guns and two 20 mm Hispano cannon in the nose.Intended for dispersed production by semi-skilled labour, the structure broke down into sub-assemblies.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.