The National Motor Museum Trust

The little round-tank BSA, with its sturdy side-valve engine, was a deservedly popular model in the 1920s. It was cheap to buy, economical to run and reliable. A two-speed gearbox with chain was first employed but later versions had three-speed gearboxes.

In 1924, BSA machines of this type were bought by the Post Office to inaugurate the telegram service (and the trend of using small BSA machines was continued throughout nearly 60 years that the service operated).