British Railways experimented with diesel multiple units from the early 1950s to try and bring down the costs of operating secondary routes. The Derby Lightweight DMUs were the first to be built in large numbers. They were built at BR’s Derby Works from 1954 to 1955 in various formations including 12 power-twin 2-car units, 84 power-trailer 2-car units, and four 4-car units. Two single-car units were originally built as a two-car unit and then split two years later to suit demand. One of the units was built as a Battery Electric Multiple Unit which was used on the Royal Deeside line in Scotland between Aberdeen and Ballater from 1958.
The first units were introduced on the Leeds to Bradford services. Subsequent units were introduced onto services in Cumbria, Lincolnshire, Norfolk, Birmingham to Sutton Coldfield, Bletchley to Buckingham and Banbury, and East London lines.
These units were an outstanding success, helping to reduce the operating costs of branchlines. So British Railways ordered many more DMUs from various builders over the next decade, thus helping to eliminate steam-hauled services. However, as the Lightweight units were not compatible with the later units, they were retired early, the last being withdrawn from normal traffic in 1969.
The Class 101 DMUs were built by Metro-Cammell at Washwood Heath in Birmingham from 1956 to 1959. This class proved to be the most successful and longest-lived of all BR’s First Generation DMUs, with the final five units being withdrawn on 24th December 2003.
The Class 105 DMUs were built by Cravens of Sheffield in five batches. Most were allocated to the ER, NER, and ScR, but Batch Two was for the LMR. This batch comprised 66 power cars and 19 trailers, forming 19 3-car sets and 14 power twins. They were ordered at the beginning of 1956 and the first vehicles were delivered in September 1957. Numbering was as follows:
The Class 108 DMUs were built by BR Derby from 1958 to 1961, with a final production quantity of 333 vehicles. The units stayed in regular service until 1990, when they began to be withdrawn from traffic. The final units lasted in traffic until October 1993, although many saw further use in departmental service, as Sandite or route-learner units.