The British Rail Class 114 diesel multiple units were built by BR Derby from September 1956 to July 1957. Forty-nine 2-car units were built, numbered E50001-49 for driving motors (later renumbered 53001-49) and E56001-49 for driving trailers (later renumbered 54001-49). 

The vehicles were the first type to be built at Derby with the longer 63 1/2ft underframe, and the first Derby vehicles to be built from steel. This design would be re-used in the 116 and 117. The type was classed a heavyweight unit; with their original 150 hp BUT engines, they were found to be underpowered for the local scheduled services, and lost time especially when towing a van (which was a regular occurrence in that area). The most problematic stretch was the 1 in 122 for just under a mile near Ancaster which reduced these units to 45 mph even on full power. As a result of this, several 3-car formations were put together using two power cars and one trailer. The type was re-engined with Leyland Albion 230bhp motors.