London Underground 1956 Stock

Before mass production of the 1959 tube stock, three 1956 Tube Stock units were built as prototypes by Birmingham RC&W, Gloucester RC&W and Metro-Cammell. These units were tested on the Piccadilly Line and remained in service after production trains were introduced. Later they were transferred to the Northern Line, but in 1995 they were replaced as non-standard by 1962 Stock cascaded from the Central Line. Planning for the stock began in the late 1940s, as the Standard stock stock running on the Central and Piccadilly lines was getting on for thirty years old and becoming due for replacement. Originally the replacement was to be called 1952 Tube Stock, but financial constraints meant that the prototypes did not become available until 1957. The production run followed in 1959. When the 1952 Stock was conceived it had been planned that the trains would be painted red. But in the early 1950s, London Underground had started constructing trains out of lighter aluminium alloy instead of steel, and were left unpainted, e.g. the later District Line R Stock trains. The unpainted exterior was adopted for the prototype 1956 stock and production 1959 / 1962 stock and the interiors were given a blue and grey colour scheme to match.