The Vickers Wellesley was a medium bomber that was designed and produced by the British aircraft manufacturer Vickers-Armstrongs at Brooklands near Weybridge, Surrey.

The Wellesley's origins stretch back to the early 1930s, during which time Vicker's management were making great efforts to secure more business in the fixed-wing aircraft sector following the decision to discontinue airship production.

[1] Several of its designs around this period, often made in response to various specifications issued by the Air Ministry, revolved around a conventional biplane configuration, albeit larger than most contemporaries and being fitted with more powerful engines to match.

While some of these proposals never went beyond the drawing board, they often harnessed the work of Barnes Wallis to save weight without compromising on strength by using light alloy structures.

[4] Following the submission of these three design outlines to Air Ministry in November 1931, it accepted the Type 253, and issued an initial development contract to Vickers during April 1932.

According to aviation author C. F. Andrews, this design choice was a radical shift from established practices of the era, which had been virtually unchanged since the First World War.

[7] Following their delivery, the Type 253 prototypes were subject to competitive testing of their fulfilment of the specification's various criteria against a range of competing aircraft, including the Fairey G.4/31, Westland PV-7, Handley Page HP.47, Armstrong Whitworth A.W.19, Blackburn B-7, Hawker P.V.4 and the Parnall G.4/31.

[10] Andrews observed that the Wellesley absorbed an abnormally high level of engineering development resources, largely due to the novel structure used throughout its airframe.

[9][14] In August 1936, the contract was revised, including a new requirement for the production model of the aircraft to be powered by the Bristol Pegasus XX radial engine.

On 30 January 1937, the first production Wellesley performed its maiden flight from Brooklands, it was delivered for type tests at RAF Martlesham Heath on 18 March.

Around this time, the RAF examined various options for improving the Wellesley, including provisions for a third crew member amidship as a navigator, while the bomb-aimers' prone position was also an area of attention.

[15] On 5 November 1938, three of these aircraft under command of Squadron Leader Richard Kellett flew non-stop for two days from Ismailia, Egypt to Darwin, Australia 7,162 miles (11,526 km) setting a world distance record.

Although obsolete, the Wellesley formed a major part of the British Commonwealth bomber forces, mainly carrying out raids targeting Eritrea and northern Ethiopia.

Three days later, they were involved in their first air combat, when Capitano Mario Visintini, future top-scoring biplane ace of the Second World War, intercepted a pair of Wellesleys from 14 Squadron on their way to bomb Massawa.