These machines were the early post war replacements for the remaining fleet of BSA M20's and Matchless GL3's which, together with the US built machines, had formed the major component of the Army's wartime motorcycle holdings.
The B40 with telescopic front forks was a modern motorcycle in its day and was used for convoy control, messenger services and the carriage of any small stores, which could be fitted into the pannier bags. The carriage of messages was an important function at a time when radios were few, and less reliable than now. Shepherding road convoys, particularly on major exercises, with the British Army of the Rhine in Germany, was a vital function. Motorcycles ensured that units did not become muddled, as there was often a set time allocation for the use of roads by military traffic with no allowances for losing the way.
The B40 like most military motorcycles of the period was basically a road machine with limited off road performance.
It is suggested that the total number supplied to the British Armed forces was 3,087, which included 135 for the RAF and 26 for the Royal Navy. BSA received a further order for an additional 235 machines in 1971, which the company was unable to fulfil due to its increasingly precarious state at the time.
As well as serving in the British Army, Royal Navy and Royal Air Force, the WD B40 was sold to the armies of Australia, Denmark, Jordan to name a few.