The Ambassador had its origin in 1943 as a requirement identified by the Brabazon Committee for a twin-engined short-to-medium-haul replacement for the Douglas DC-3. Airspeed Ltd. was asked to prepare an unpressurised design in the 14.5-ton gross weight class, using two Bristol Hercules radial engines. In 1943, the company duly set up a dispersed design office in Fairmile Manor at Cobham in Surrey.
By the time the British Ministry of Aircraft Production ordered two prototypes from Airspeed, immediately after the end of the Second World War, the design had grown substantially. The Ambassador would be pressurised, have more powerful Bristol Centaurus radials and have a maximum gross weight of almost 24 tons.
The revised design offered seating for 47 passengers and, having a tricycle undercarriage, looked more modern than the DC-3s, Curtiss Commandos, Avro Lancastrians and Vickers Vikings that were common on Europe's shorter airline routes. With three low tailfins and a long pointed nose, it shared something of the character of the larger transcontinental Lockheed Constellation.
Great efforts were made to reduce drag, to improve performance and cruising efficiency. The engine nacelles were first designed with inwardly opening louvres for exhaust gases and cooling air rather than the usual outwardly opening "gills". However, these proved inadequate to cool the engine, so the gills were reinstated.
Three prototypes were built, the first registered G-AGUA was first flown by George B.S. Errington from Christchurch on 10 July 1947. British European Airways (BEA) placed a £3 million order for 20 aircraft in September 1948, and operated them between 1952 and 1958, calling them their "Elizabethan Class" in honour of the newly crowned Queen. The flagship of the fleet was G-ALZN, appropriately named "RMA Elizabethan". The first "Elizabethan" scheduled flight was from Heathrow to Paris Le Bourget on 13 March 1952 and the type later also served the key UK routes. By December 1955 the "Elizabethan Class" had reached 2,230 flying hours annually, per aircraft, the highest in BEA's fleet. However, the last Elizabethan scheduled service for BEA was operated in August 1958, and the type was replaced by the Vickers Viscount.