Development of the Argosy originates in the AW.66, a proposed twin-engined military transport that was designed with British Air Ministry's Operational Requirement 323 (OR323) in mind.

First flown on 4 March 1961, this model featured double the range of the Series 100 and otherwise differed by an alternative door arrangement, which was largely to facilitate paratroop operations.

First flown on 11 March 1964, this model featured a new wing incorporating a fail safe structure, being stronger and lighter than its original counterpart.

However, a lack of available finance contributed to the company's decision to abandon all work towards meeting the military requirement; despite this setback, Armstrong Whitworth had already decided to proceed with developing the civil variant as a private venture.

[2] The company believed that the type would have significant appeal to the growing short-haul air freight sector of both the European and American markets.

[4] As work continued, the AW.65 was extensively redesigned, including the adoption of four Rolls-Royce Dart turboprop engines; the resulting aircraft being designated as the AW.650.

[6] In December 1960, the Argosy received type certification from the American Federal Aviation Administration (FAA), authorising the aircraft's entry to commercial service.

[8][4] While the RAF had lost interest in any acquisition of the original AW.66 design, the service still needed to procure a replacement for its obsolete piston engined transport fleet, including the Vickers Valetta and Handley Page Hastings.

The revised version, designated as the Series 200, also featured several other improvements, including the adoption of enlarged cargo doors, integral wing fuel tanks and a modified landing gear arrangement.

[4] In the cargo role, the Argosy was designed for rapid turnaround times of only 20 minutes without the use of lifting trucks or cranes, utilising pallets and rollers to eliminate packaging.

[19] In terms of its basic configuration, the Argosy's tailplane was mounted on twin booms that ran rearwards from the inner engine nacelles, leaving the cargo doors at the rear of the fuselage clear for straight-in loading.

[17] The sound produced by the Dart engines combined with its relatively unusual "pod and boom" basic configuration, which was similar to the earlier C-82 Packet and C-119 Flying Boxcar transport aircraft, has been attributed as the source of the type's nickname "The Whistling Wheelbarrow".

Reportedly, the Argosy had contributed to BEA possessing a superior air freighting ability to any other airline operating in the region, the type's double-end loading capability being a viewed as a crucial part of its economics.

[6] During April 1970, BEA opted to withdraw its Argosy fleet, choosing to replacing the type using a freighter conversion of its Vickers Vanguards.

[24] During April 1990s, one of these aircraft was damaged beyond repair as a result of a landing accident; a third Argosy was leased by SAFE Air from Australian company Mayne Nickless for five months during 1990 as a short-term replacement.

[25] During 1991, the last operational Argosies, which was being flown by American cargo airline Duncan Aviation, were withdrawn, marking the end of the type's flying history.

Operationally, it could carry various items of military equipment, including combat vehicles such as the Saracen or Ferret armoured cars, or artillery such as the 105 mm (4.13 in) howitzer or Wombat.

Additional differences to the civil variants:[31] 56 aircraft were produced for the RAF under the designation Argosy C Mk 1 (C.1), it served in a total of six squadrons; three based in the UK and one each in Aden, Cyprus, and the Far East.

After the removal of the Argosy C.1 from the cargo/transport role, it was decided to modify 14 aircraft[32] as Navigation Trainers for RAF Training Command, which were intended to replace the Vickers Varsity.