The Armstrong Whitworth Argosy derived from Air Ministry Operational Requirement 323 of 1955 which called for a medium-range aircraft capable of carrying a payload of 10,000 lbs over 2,000 miles. Whilst a lack of funds cancelled the military requirement, Armstrong Whitworth pursued a civil variant designated the AW650 as a private venture. Re-named the Argosy, the first machine made its maiden flight on 8th January 1959.
The RAF still needed a replacement for the Hastings, however, and in 1959 the Air Ministry issued a specification for a military derivative of the AW650 to serve as a medium-range transport and paratroop aircraft. Powered by 4 x Rolls-Royce Dart 101 turboprop engines, the significantly different AW660 first flew on 4th March 1961. Fitted with a stronger floor than the civil version, ‘clamshell’ rear doors and an integral loading ramp, this military variant was capable of carrying 69 troops, 54 paratroops, 48 stretcher cases or 29,000 lb of freight (which could include Saracen/Ferret armoured cars or artillery pieces such as the 105 mm howitzer). It entered service as the Argosy C1 with Nos 114 and 267 Squadrons at RAF Benson and No 105 Squadron RAF Khormaksar in 1962 and a year later with No 215 Squadron at RAF Changi. The aircraft continued in front-line service until February 1975 when the last squadron operating the type was re-equipped with the Hercules. Nine C1s converted in 1971 to meet the RAF requirement for a flight inspection aircraft continued operating until 1978.
A total of 73 Argosies were built of which 56 were military C1s. Several survivors are on static display at museums in the UK and USA with a civilian version on display in New Zealand.