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Derby Lightweight power car no. 79018 on display at Bewdley on the Severn Valley Railway on 15th October 2004, as part of the Railcar 50 event. This vehicle has been restored to its original condition using a grant from the lottery heritage fund, and is preserved at the Midland Railway Centre.

Derby Lightweight trailer no. 975008 (79612) on display at Bewdley on the Severn Valley Railway on 15th October 2004, as part of the Railcar 50 event. This vehicle has yet to be restored to original condition, and is preserved at the Midland Railway Centre.

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 two single car units, 12 power-twin 2-car units, 84 power-trailer 2-car units, and four 4-car units. Contemporaneous with these units was the unique Battery Electric Multiple Unit.

The first units were introduced on services around the West Riding of Yorkshire, namely Leeds to Bradford services. Subsequent units were introduced onto services in Cumbria, Lincolnshire, Norfolk, and Birmingham to Sutton Coldfield, Bletchley to Buckingham to Banbury, and East London lines services.

These units were an outstanding success, helping to reduce the operating costs of branchlines. As such, British Railways ordered many more DMU vehicles from various builders over the next decade, thus helping to eliminate steam locomotives. However, as these units were non-standard compared other later DMU vehicles, they were subject to early retirement. The last units were withdrawn from normal traffic in 1969.

Four different sorts of formation were created from the 217 cars built of this type, as follows:

Power Twins:

DMBS    DMCL       DMBS    DMCL
79000 + 79500  to  79007 + 79507
79184 + 79189  to  79188 + 79193

Power Trailers:

DMBS    DTCL       DMBS    DTCL
79008 + 79600  to  79033 + 79625
79034 + 79250  to  79046 + 79262
79118 + 79639  to  79141 + 79662
79142 + 79684
79143 + 79663  to  79149 + 79669
79169 + 79670  to  79181 + 79682

Four Car Units:

DMS     TBSL    TSL     DMC
79150 + 79325 + 79400 + 79508
79151 + 79326 + 79401 + 79509
79152 + 79327 + 79402 + 79510
79153 + 79328 + 79403 + 79511
79154 + 79329 + 79404 + 79512

Single Car Units:

DMBS
79900
79901

79683 was left over as a spare DTCL, and took the place of 79649 in 1957, when this was converted into a special saloon. It was later renumbered 999510 in the departmental saloon series and was eventually scrapped in 1981.

In 1962 three of the power twin units were converted to power trailer units, when 79191-79193 were rebuilt as DTCL vehicles and renumbered 79633-79635.

• Engine: Two BUT (Leyland) 125 bhp
• Transmission: Hydraulic, Lysholm Smith (Leyland) torque converter
• Coupling code: Red triangle

• Engine: Two BUT (AEC) 150 bhp
• Transmission: Mechanical
• Coupling code: Yellow diamond

A number of cars from these units were subsequently transferred to departmental (non-revenue earning) use after withdrawal from normal service:

• 79018 + 79612 were rebuilt as an ultrasonic test train based at Reading, numbered 975007 + 975008. Replaced by unit 901001.
• 79900 was rebuilt as test coach "Iris", based at Bletchley, numbered 975010. Later transferred to the BR Research Division at the Railway Technical Centre at Derby, for its last few years in traffic, it was repainted into original BR Green livery. Replaced by unit 901002.
• 79185 was taken into departmental use for brake trials, numbered 975012. It was scrapped in 1970.
• 79250 and 79252 were taken into departmental use as staff messrooms, numbered 975013 and 975014. They were scrapped in 1978 and 1982 respectively.
• 79649, the inspection saloon mentioned above, took its place in the departmental series as 999510.

Thanks to their extended life in departmental service, one 2-car unit and a single car unit survive in preservation, the former following a high-profile campaign.

• History of the Derby Lightweights