The Wellesley evolved from Vickers' design for a general-purpose day and night bomber and coastal-defence torpedo-carrier biplane to satisfy Air Ministry Specification G.4/31, the company having decided to develop and build a monoplane aircraft to meet the same specification. When evaluated there was little doubt that the monoplane was superior, with the result that the Air Ministrv contract for the biplane was cancelled, being replaced on 10 September 1935 by one for 96 examples of the monoplane under a rewritten G.22/35 specification.

Named the Wellesley, it was the first RAF aircraft to utilise the geodetic form of construction devised by Barnes (later Sir Barnes) Wallis; offering a lightweight structure of great strength, it was adopted later for the Wellington. The other highly unusual feature was the provision of a pannier beneath each wing to serve as a bomb container. The low-set monoplane wing was also of geodetic construction, the main landing gear was hydraulically retractable, and power plant comprised a single Bristol Pegasus radial piston engine.

Wellesley Mk Is entered RAF service in April 1937 but by the outbreak of World War II most of them had been transferred to the Middle East, where they remained operational into 1941. The type is remembered especially in service with the RAF's Long Range Development Flight, which was established at RAF Upper Heyford, Oxon, in January 1938. Equipment comprised six Wellesleys modified by the installation of Pegasus Mk XXII engines installed in NACA long-chord cowlings, and driving constant-speed propellers; plus other changes which included strengthened landing gear, increased fuel capacity and the introduction of an autopilot. Between 5 and 7 November 1938, two of a flight of three of these aircraft (led by Sqn Ldr R. Kellett) succeeded in establishing a new world long-distance record, covering non-stop the 11,526km between Ismailia, Egypt, and Darwin, Australia, in just over 48 hours.

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A three-view drawing (1000 x 1510)