What did Specification B.14/46, which gave rise to the V bombers, call for?

In January 1947 the British Ministry of Supply circulated Specification B.35/46 to industry, responding to Air Staff Operational Requirement OR.229: a medium-range land-based bomber capable of carrying a 10,000 lb (4,500 kg) bomb to a target 1,500 nautical miles (2,800 km) away from a base that could be located anywhere in the world. It called for a cruising speed of 500 knots (930 km/h) at altitudes between 35,000 and 50,000 ft (11,000 and 15,000 m), and a maximum take-off weight not exceeding 100,000 lb (45,000 kg). As an alternative, the aircraft had to be able to carry 20,000 lb (9,100 kg) of conventional bombs.

Six companies submitted proposals, including Avro, whose Type 698 would eventually become the Vulcan. A parallel requirement, OR.230, called for a long-range bomber with a 2,000 nautical mile radius of action, but that was deemed too demanding.

B.14/46 was a less ambitious specification. As insurance in case the radical designs failed, Short Brothers received a contract for the SA.4 prototype under that specification. The SA.4, later named Sperrin, ultimately proved unnecessary.

In April 1948 Vickers received authorization to proceed with its Type 660, which did not fully meet the requirements of B.35/46 but had a more conventional design and could be ready sooner. That aircraft entered service as the Valiant. Together with the Vulcan and the Victor, it formed the family known as the V bombers.

The first prototype flew on 30 August 1952, and the RAF received its first Vulcan B.1 in September 1956.