During WW2 Balham, at a depth of 30 feet, was one of many deep tube stations designated for use as a civilian air raid shelter. It sheltered hundreds of people each night.
At about 8pm on 14 October 1940, a 1,400kg semi-armour piercing fragmentation bomb fell on the road above the northern end of the platform tunnels, creating a large crater into which a bus then crashed. The northbound platform tunnel partially collapsed and was filled with sand, rubble and water from the fractured water mains and sewers above, which also flowed through the cross-passages into the southbound platform tunnel.
The torrent burst onto the platforms. and people were swept away. 600 people were rescued but more than 60 civilians and London Transport staff were killed.
World War II Today has more details and photographs. The incident features in Ian McEwan's novel 'Atonement'. This and the subsequent film both use an incorrect date.
London News Online has another, colour, photo of this scene, from a different angle.
Credit for this entry to: Alan Patient of www.plaquesoflondon.co.uk
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