London's Metropolitan Railway became the world's first underground passenger line when it opened in January 1863. Electric locomotives were first used on the London Underground when the first deep-level tube line, the City and South London Railway, was opened in 1890.

In 1933 the London's underground railways, tramway companies and bus operators to form … From 1864, the MR bought steam locomotives of its own, which operated over its own tracks and those of the Metropolitan District Railway. The first underground railways in London, the Metropolitan Railway and the District Railway, used specially built steam locomotives to haul their trains through shallow tunnels which had many ventilation openings to allow steam and smoke to clear from the tunnels.

Through running of various mainline company locomotives continued into the 1960s. London Transport numbered all of its service stock locomotives into one unified series, regardless of the type. Metropolitan Railway A Class 4-4-0T, 1864 Metropolitan Railway B Class 4-4-0T In 1933 the Metropolitan Railway was absorbed into the newly created London Passenger Transport Board and on 1 November 1937 the later G, H and K Class steam locomotives were transferred to the London and North Eastern Railway (LNER) who took over all freight workings and became responsible for hauling passenger trains with steam locomotives north of Rickmansworth. In 1933, London's underground railways, tramway companies and bus operators merged to form the London Passenger Transport Board(LTPB), commonly known as London Transport. It was impractical to use steam locomotives … London Underground steam locomotives.