[2] At the outbreak of World War II BSA were Britain's largest motorcycle manufacturer with a long history of armaments supply to the armed forces.

Designed by Val Page the BSA M20 started development in 1937 as a heavy-framed sidecar model with a simple 500 cc single cylinder side valve engine.

The factory was one of the main targets for the Luftwaffe and at 9.25pm a low flying aircraft dropped two bombs which destroyed the southern end of the BSA building in Armoury Road.

In 1941 front and rear number plates were removed and between 1941 and 1942 active service use in North Africa showed the need for easy adjustment of the fork dampers.

[3] From 1942 there was a shortage of rubber so handlebar grips and foot pegs were replaced by canvas covered metal items and production was standardised, with only minor modifications until the end of World War II.

In 1943 further modifications were made including redesign of the crankcase sump shield and fitting of the Vokes high capacity air cleaner, which was a box shaped canister on top of the fuel tank and was intended to assist operations in dusty environments.

A 1938 BSA M20 ridden by Bill Jenkins from Dallas achieved a top speed of 108 mph at Bonneville Salt Flats making it the fastest M20 in the world.

The motorcycle did however retain the long BSA prop stand that hinged under the seat and clipped to the rear mudguard when not in use — so it looked like a stock M20.

[9] In October 1995 an M20 fitted with a BSA Gold Star crankshaft sprocket and running on a 95% methanol / 5% acetone mix ridden by Pat Jeal achieved a terminal speed of 112 mph at the disused airfield of RAF Elvington, Yorkshire.