To meet the requirements of Specification F.7/30 for a four-gun day and night fighter powered by the Rolls-Royce Goshawk engine using evaporative cooling, Westland schemed a parasol monoplane in continuation of the Wizard concept, but found it impossible to combine the required slow landing speed with the 402km/h maximum. An alternative biplane, the P.4, was successfully tendered, however, one prototype being ordered in 1931. With a 600hp Goshawk VIII buried in the fuselage behind the pilot, driving the propeller via a long extension shaft, this single-bay biplane featured a gulled upper wing with short inboard struts in place of the usual cabane, and a staggered lower wing of slightly shorter span. When first flown on 23 March 1934, the F.7/30 had an open cockpit, but a full canopy was soon added. Armament of four 7.7mm Vickers guns was concentrated in the nose. Construction was of metal throughout, with metal skins for the forward fuselage and engine bay, and fabric elsewhere. Ailerons were fitted to the upper wing only, this also having Handley Page slots.
Although it handled well, the F.7/30 was found deficient in performance when tested at Martlesham Heath, and no further development occurred.
Max take-off weight: 2359 kg / 5201 lb
Empty weight: 1672 kg / 3686 lb
Wingspan: 11.73 m / 39 ft 6 in
Length: 8.99 m / 30 ft 6 in
Height: 3.28 m / 11 ft 9 in
Wing area: 34.37 sq.m / 369.96 sq ft
Max. speed: 298 km/h / 185 mph