But why, when underground travel plays such a vital role in keeping London moving, did they close? The answer lies in the fact that, originally, the Tube didn't work as an integrated system, growing organically as a series of privately-run lines.

By the middle of the 19th century, London was paying a heavy price for its success as the centre of a huge Empire. Every day increasing numbers of commuters were flooding in from both the suburbs and the city's national-network stations, putting a massive strain on a tram system that was already struggling to get people from A to B.

Unplanned expansion

The first sections of what we now recognise as some of the Tube's key lines – the Metropolitan (1863), the Central (1900), the Piccadilly (1906), the Bakerloo (1906) and the Northern (1907) – were built in response to this crisis. Effectively, this era was a transport gold-rush, with companies competing to secure their share of the large profits to be made in moving people quickly around town.

The system's unplanned growth meant that central London quickly became peppered with underground stations, many within only half a mile of each other, and few offering connections between lines. By the outbreak of the first world war, most of these lines were affiliated as part of the Underground Group, but after hostilities had ended a parliamentary select committee was still critical of what it called the transport system's "acute and wasteful competition", poor services and high fares. It took until 1933 (the year Harry Beck's new map was unveiled) for all of London's transport – buses, trams, underground and trains – to be put under the central control of the London Passenger Transport Board.

The 1930s marked the second major period of expansion for the Tube system, as the Northern, Bakerloo and Piccadilly Lines were driven out into the suburbs. These extensions meant that commuters began to feel the slowing effect of central London's tightly-packed stations – it made their journeys to and from work unbearably long. As a result, some stations were taken out of service, for example, the Piccadilly Line shed both Down Street (off Piccadilly) and Brompton Road (between Knightsbridge and South Kensington).

Wartime bunkers

Down Street station was a particular victim of bad planning. Built out of sight of the main road, extremely close to the station at Hyde Park Corner and in an area where rich residents judged underground travel "inappropriate", it had never attracted enough users. It was closed in 1932, but as hostilities in Europe increased, was soon converted into a bunker headquarters for the Railway Executive Committee. Churchill also chaired the War Cabinet at Down Street a number of times, commenting that he always slept well in what he nicknamed The Burrow. Other stations had to be lost to tighten-up system connectivity: the British Museum station (one stop east of Tottenham Court Road on the Central Line) was closed in 1933 when new platforms were built at Holborn to make a below-ground interchange between the Central Line and the existing Piccadilly Line station.

Shoreditch shuts

Closures have continued ever since, the most recent being Shoreditch, in the summer of 2006, as part of the development of the East London Line. But what has happened to the "ghost stations" these closures create? As system costs leave virtually no money for stripping out disused spaces, London Transport has left many of them more or less intact, creating a series of architectural time capsules, deep underground.

For security reasons all of the abandoned stations, except for Aldwych (which is used for commercial filming and as a training space for the London Fire Brigade), have been sealed off from the surface – they are accessible only via the tracks, and many are used for storage. But to Tube users, bricked-up sections of tunnel, or a particularly long run between stations (for example, the stretch of the Piccadilly line between Kings Cross and Caledonian Road used to be filled by a station called York Road) are the only signs that these stations ever existed.