One of London Underground’s rarest and best preserved signal boxes has been given a Grade II listed status today as a result of a joint English Heritage and Network Rail project to safeguard railway signalling heritage.

This box is the only remaining historic signal box on the central London underground lines.


The signal box is a building type unique to railways, although with a precursor in the shape of the semaphore towers erected during the Napoleonic Wars. Signal boxes originated in the 1840s, with signalling platforms accompanied by a basic hut or cabin provided for the men operating railway signals. The signal box as we know it today – a covered and glazed structure housing levers which control both signals and points – was the invention of John Saxby, who pioneered the mechanical interlocking between points and signals which he patented in 1856.

The signal box being listed today is based at Liverpool Street station and came into use on the 1st February 1875, when the Metropolitan Railway completed the third phase of its extension from the original Underground terminus in Farringdon.

The extension had been started in 1873, but after construction exposed burials in the vault of a Roman Catholic chapel, the contractor reported that it was difficult to keep the men at work, so it took 2 years to dig the line just one stop from Barbican to Liverpool Street, or Bishopsgate as it was known at the time.

The first section opened as far as the Great Eastern Railway’s (GER’s) recently opened terminus at Liverpool Street on 1 February 1875. For a short time, while the Met’s own station was being built, Underground trains ran into the mainline station itself via a curve, the Met opening its station later that year on 12 July and this curve has not being used again by regular traffic.

The signal box was a bespoke design for the Metropolitan Railway by McKenzie and Holland, unusually having glazing on all sides because of its location on what was originally a junction. Its survival at a central London railway terminus is unique.

In use as a signalling box since it opened, it was converted into an Interlocking Machine Room in December 1956, and controlled from Farringdon until March 2001 when control was transferred from Baker Street control room.

It is still in use as the remote controlled machine box.

Two other London Underground signal boxes are listed — at Chesham (1889) and Ruislip (1904), both Metropolitan Railway designs.


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  1. Tom Rainbow says:

    I want to know:
    1) if the little house in the triangle of lines is available to buy – I fancy living in a railway house, and
    2) Is the gap in the houses near the water pumping station in Cricklewood the remains of a reversing siding for trains. Anyone know?

  2. Tom Rainbow says:

    Oops – should have said the little house in Neasden.

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