5700 Class - L91 - London Transport MaroonLondon Transports 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