The British Rail Derby Lightweight diesel multiple units, were the first such trains to be built en-masse for British Railways. The units were built at BR's Derby Works from 1954 to 1955. The units were built in various formations, including 12 power-twin 2-car units, 84 power-trailer 2-car units, and four 4-car units. The two single car units were originally built as a two-car unit and then split two years later when demand came about.

Body framing was extruded and riveted together. Panelling was welded into continuous sheets and riveted to the frame. Luggage racks were light alloy. The floors had 2 layers of flameproof hardboard, covered with linoleum. To reduce noise and condensation, the inside structure and undersides were sprayed with asbestos. Lighting was by 60-watt, 24-volt lamps charged by belt driven dynamos. Heating was oil fired. Standard mild steel bogies ran on Timken roller bearings.