The Air Ministry published Specification B.12/36, for a high-speed, long-range four-engined strategic bomber aircraft, that would be capable of being designed and constructed at speed. The bomb load was to be a maximum of 14,000 lb (6,350 kg) carried to a range of 2,000 miles (3218 km) or a lesser payload of 8,000 lb (3,629 kg) to 3,000 miles (4,800 km) (very demanding for the era). It was to have a crew of six and was to have a normal all-up weight of 48,000 lb, while a maximum overload weight of 65,000 lb was also envisioned. The aircraft would have to be capable of cruising at speeds of 230 mph or greater while flying at , carrying three gun turrets (located in the nose, amidships and rear positions) for defence.