Introduced in August 1939, the Bedford OB chassis was designed specifically for public transport. The off-set differential on the rear axle combined with the mounting of the engine and the gearbox at a slight angle permitted a sunken, central gangway for easier passenger access. However two months later, following the outbreak of World War II, production was stopped after only 73 chassis had been manufactured. In January 1942, production of a more utilitarian version known as the OWB recommenced.In October 1945, production of the OB resumed and the Bedford OB chassis went on to play a major role in the re-equipping of many transport fleets as demand rose sharply.
Over 40 different coach-builders used the chassis, but by far the biggest was the Hendon-based firm of Duple, whose Vista body was to become synonimous with the
During 1947, the destination and fleet-name boxes were modified,a rounded outer edge replacing the earlier angular one. In 1948, due to material shortages, the characteristic side “flash” was omitted and replaced by a single aluminium bead about 3 inches below the waistline, and the operator's name plate box was removed from the rear. The original 4-spoked steering wheel was replaced by a 3-spoked version. In 1949, the side flash and the operator's plate returned. Later that year, the luggage door locks, which had been operated by a T-key, were replaced by a single locking handle and the rear direction indicator lights were changed. The large chromed bumper over-riders were removed, a deeper rear bumper/body trim was added which incorporated the wording