As the Battle of Britain turned in to the Blitz in October 1940, the British Government, who had initially tried to prevent people using tube stations for shelter, embarked on a project to construct dedicated deep-level air raid shelters in London.
Despite the urgency of the situation, London Transport was consulted about their design and locations, with the forward-thinking intention that they could be linked up after the war and used as a new railway line. A route adjacent to the existing Northern line was chosen, in anticipation of creating an express version of this line with fewer stops.
The shelters, each almost half a kilometre long, were constructed in parallel pairs (for the two tracks of a future railway that never materialised) at Clapham South, Clapham Common, Clapham North, Stockwell, Goodge Street, Camden Town and Belsize Park. An eighth shelter was built at Chancery Lane, which could have been integrated in to an express version of the Central line.
All of the shelters were completed in 1942, each with capacity to accommodate 8,000 people across two levels in two tunnels, but they were not immediately opened as bombing has subsided by then. Clapham South was initially used as weekend troop accommodation but was finally opened to the public in July 1944, amidst the V-1 flying bomb campaign.
It closed ten months later, once the V-1 campaign had finished. In 1948, it was briefly used to house up to 200 migrants who had arrived from the Caribbean on the Empire Windrush, before they found jobs and accommodation throughout South London, and beyond. In this way, the shelter was a key component to the cultural and social diversification of the area.
Three years later, this shelter was bullishly rebranded as the Festival Hotel and provided cheap B&B accommodation for visitors to the Festival of Britain, with London Transport even offering a temporary bus route straight to the Festival Gardens in Battersea Park.
Commonwealth troops were housed in the shelter again during the 1952 funeral of King George VI and subsequent coronation of Elizabeth II, a year later.
Since then, the shelter has been leased by a private company for secure document storage but the Government has recently sold it to Transport for London.