After supplying thousands of motorcycles to the British armed forces during the First World War, BSA continued to grow in the ensuing years of peace, eventually becoming the largest manufacturer of such vehicles in the United Kingdom.
Given its industrial capacity and prior military experience, in 1936 BSA submitted a model for the competition to supply a standard motorcycle for the British Army. The basis was the civilian M20, designed by the renowned Val Page (who had previously worked for JAP, Ariel and Triumph). It featured a heavy, robust frame, a simple single-cylinder side-valve engine and a capacity of 500cc. Nevertheless, the proposed model failed to impress the procurement board.
In fact, BSA only saw one of its models selected in 1938 — a modified WM20 version adapted for military service, distinguished by the addition of a large eight-inch Lucas DUl42 headlamp fitted with the inevitable blackout cover.
From an initial rejection, this same motorcycle evolved into the most distinguished and widely produced model supplied to the British War Office. At the outbreak of the conflict, the government requisitioned the 690 motorcycles BSA had in storage and ordered a further 8,000 WM20s. The vast majority were delivered to the Army, though smaller numbers were also used by the Royal Navy and the Royal Air Force. Interestingly, many BSA motorcycles supplied to the Air Ministry were fitted with sidecars made by the Swallow Sidecar Company, founded by William Lyons — a firm that, after the war, would change its name to Jaguar.
Although Val Page had designed it as a general-purpose motorcycle for convoy escort, messenger and liaison duties, the WM20 was used in every theatre of war and for virtually every conceivable purpose, owing to the sheer number produced (a total of 126,334 units). Motorcyclists could travel far more swiftly than four-wheeled vehicles, particularly across rough terrain or through bomb-damaged cities. Thanks to its outstanding performance, the BSA WM20 became known for its robustness and ease of maintenance, earning a reputation as one of the most reliable motorcycles in Allied service.
After the war, the WM20 remained in military use well into the 1960s, most examples having undergone numerous mechanical overhauls and rebuilds. Many BSA WM20s still survive today, though few remain in entirely original condition due to their long operational lives. Having served during the war on the island of Malta, this particular example features the traditional sand-coloured 8th Army Desert Yellow paint scheme.