London Transport’s railway network is well known for being electrified and “underground” but there had always been a small fleet of steam locomotives retained for working infrastructure trains on the surface lines. By the 1950s, these older locomotives were well past their prime and London Transport began to look for replacements. Diesel locomotives were considered, as was a small fleet of ex GNR J52 steam locomotives but their trial was unsuccessful. In 1956, the solution came in recently withdrawn ex GWR 57xx pannier tanks.

Modifications were required to the cab roofs to allow for tighter clearances which involved removing the protruding roof section and placing a new rainstrip higher on the roof. Modifications were also required to fit the locomotives with “trip cocks” to be compatible with LT’s signalling system. These cocks would contact a ramp which was raised at red signals causing a loss of vacuum brake and stopping the train. Extra brackets were fitted on the running plate, and the cocks were fitted to these. Steam heat was not a requirement for the engineering trains so this was removed. In total 13 locomotives were bought by LT although only 11 ever ran at once.

L91, as modelled was actually the second locomotive to carry the number L91. Originally this running number was allocated to ex GWR number 5752, a 1929 vintage product of Swindon Works. This was one of the first to enter traffic with LT in 1958 but when it required repair in 1960, costs were prohibitive, and it was scrapped and replaced with the second L91 which we have modelled here. The second L91 was actually from the same batch, ex GWR 5757, this locomotive differed to the first in that it didn’t have the top feed fitted and retained its back feed boiler right up to its final withdrawal in 1968. Unfortunately, L91 was not a survivor and was cut up by Chesterfield Steelbreaking and dismantling limited during 1970.