One exception to this was made by the City and South London Railway, who used a trailer car to hold the batteries, and wired them to a separate locomotive.

From 1936, battery locomotives were built as new vehicles, although in most cases, some components, particularly the bogies and motors, were refurbished from withdrawn passenger cars.

The batch of nine vehicles supplied by Gloucester Railway Carriage and Wagon Company between 1936 and 1938 set the standard for subsequent builds.

The manufacturer was W. R. Renshaw and Co Ltd, who were based in Stoke-on-Trent in Staffordshire, and the vehicles were fitted with current collector shoes, so that they could draw power from the rails when it was available.

[2] During the First World War, they were used as shunting engines at Ealing Common Depot, where power was always available, and so the batteries were removed, and subsequently neglected.

[4] When the City and South London Railway was being reconstructed in 1922, a number of "padded cell" trailer cars – so-called because of their lack of windows – were stripped out, so that lead-acid batteries and charging resistances could be placed in the resulting space.

Recharging was arranged at certain points, by means of switches and cables connected to the supply that normally fed the rails.

Both types, when pulling a 200-ton ballast train, could run at 30 mph (48 km/h) when supplied with power from the current rails, and at half that speed when working on batteries.

[6] The metadyne-fitted locomotives had new bodies, but the bogies and motors were removed from redundant Metropolitan line stock and refurbished at Acton Works.

For cable laying work, the metadyne-equipped locomotives could pull trains of 100 tons at 3 mph (5 km/h) for considerable distances, without any sign of overheating.

One important improvement was the addition of runners and a lifting device, which enabled any battery cell to be removed from its rack and lowered to the ground through an aperture in the floor.

This feature meant that the batteries could be changed without using an overhead crane in a lifting shop, freeing it for more important work.

This vehicle was initially numbered L76, and took part in the Metropolitan Railway centenary celebrations, held on 23 May 1963, when it propelled a replica of the original inspection train of open wagons used by William Ewart Gladstone and other dignitaries.

The locomotives have a cab at each end and are built to the standard 'Tube' loading gauge so that they can work over all lines on the London Underground network.

They were also fitted with a 'Ward' coupler, mounted at a height suitable for tube cars, but this made the locomotives prone to significant damage in shunting accidents.

Following the withdrawal of steam engines, the vehicles often worked on open sections of line, rather than in tunnels, and the need to heat the cabs in winter became apparent.

[15] The original livery was grey, but crimson lake was applied from the early 1960s using supplies of LT steam locomotive paint.

[17] All battery locomotives are fitted with tripcocks which are operated by trackside equipment if the train passes a signal at danger.

When they were built, locomotives L25 to L32 were fitted with Automatic Train Operation (ATO) equipment, which allowed them to work on the Victoria line.

The tripcock could be isolated, and a trip valve performed a similar function, except that it was operated by the ATO controller.

A special setting was provided that allowed the vehicles to move if they were not receiving safety track signals, but the maximum speed in these circumstances was limited to 10 mph (16 km/h).

[11] Subsequently, some locomotives (L27–L32) have been fitted with a new type of Victoria line ATP equipment which was designed by Metronet on behalf of Transplant, the operator of the fleet.

The traditional use of these locomotives has been to haul trains using power from the rails until they reach the area where work is to be undertaken, where they switch to battery operation if the traction supply has been isolated.

They are used for hauling materials and equipment and were specially designed and built for work in narrow tunnels with tight curves and steep gradients.

Under normal use this is not a problem because they are designed to work on engineering projects in tunnels where the power is cut off anyway, but it does mean they have to return to the depot to be recharged.