It was fitted with a 28 RAC tax horsepower petrol engine, a four-speed manual gearbox and a fully floating rear axle.

The ash framework was reinforced with steel, and the floor made from hardwood with softwood tongued and grooved boarding, with the exception of the cab area which was finished with alloy chequerplate.

[1] Geared to reach speeds of at least 40 miles per hour (64 km/h), which was fast for its day, the OB is remembered by many for its characteristic gearbox whine.

The six cylinder overhead valve power unit with a capacity of 3519 cc, introduced in 1938, developed 72 bhp (54 kW; 73 PS) at 3000 rpm.

The Bedford OWB chassis was produced during the war to the same basic design as the OB, but replacing valuable metals, like aluminium, with cast iron, and fitted with austere bodywork and interior featuring 32 seats with no upholstery, just wooden slats like a park bench.

[5] To celebrate its 70th anniversary, on 30 August 2009, a gathering was held at the Vauxhall Heritage Centre in Luton with OBs on display, before making a road run to Bletchley Park.