The BSA Bantam was one of the most successful lightweight bikes ever to be built in the UK. BSA launched the D1 in March 1948 and the first production bike was ready in June of that year. The D1 was originally built for export, but by October it was given the name Bantam and introduced to the home market. Incredibly, BSA continued to manufacture the Bantam with various upgrades and model changes until 1971, although production in D1 specification ceased in 1963.

The Bantam was not a British design, but was actually an almost exact copy of German manufacturer DKW's RT125. DKW were highly instrumental in the evolution of two stroke technology and after the Second World War the DKW designs were taken over as part of the war reparations. The major problem this caused BSA was that the gear change and kick-start were, as they are on European bikes, both on the left hand side of the bike and of course they needed them on the right for use in Britain. The answer to this problem was simple, BSA merely flipped all the design drawings, creating a mirror image of the original DKW RT125. One other significant change that was made was to convert the dimensions from centimeters to inches so the BSA factory could work on the mechanics with ease.

The first Bantam models were made from a rigid welded steel tube frame, with simple telescopic undamped front forks. The mudguards are distinctively large, especially at the back, and the front carries a number plate on both sides. The Bantam's original price tag was £60, and for the money the 123 cc 4.5 bhp engine gave a top speed of around 50 mph and an extremely economic 120 mgp. After 1950, BSA made some changes for the better, giving the Bantam a new generator, a new stand and other minor mechanics that all added to the driveability of the bike.

All Bantams were painted almost entirely in Mist Green, except for the cream colored panels on the sides of the petrol tank, which show the BSA name. The transfers with the logo were originally the simple, yet well known, BSA 'flying wing' but on later bikes, like the one in the Mathews Collection, the image was changed to incorporate the word Bantam and the picture of a rooster.