04/30/2009. Remarks by Ray Watkins: The Westbury was designed to comply with the Air Ministry Specification 4/24 which, along with the Bristol Bagshot, received a development contract (No 542527/24) in June 1925 for two prototypes, J7765 to J7766. Specification 4/24 called for a multi-seat, twin-engined fighter with a maximum speed of 125 mph (201 kmh) which could carry a heavy caliber automatic cannon to defeat similar aircraft operated by opposing forces.
The photo shows the first prototype with 450 hp
Bristol Jupiter VI nine-cylinder radial engines."