In a corner of Wiltshire - deep underneath the Cotswolds - is a network of tunnels and rooms that would have housed the British government in the 1960s in the event of a nuclear attack.
The dark and dusty underground complex near Corsham has remained relatively untouched since the height of the Cold War.
But if the crucial moment had come - would ministers have pressed the UK's nuclear button?
Here, historian Professor Peter Hennessy tours the Corsham bunker for BBC Radio 4and finds out if the former Labour Defence Secretary Denis Healey, and the late Prime Minister Sir James Callaghan, would have retaliated in the event of a Soviet nuclear attack.
Click 'show captions' for photograph details. Not all images have captions. Bunker photographs taken from the BBC Wiltshire archive.
In 'The Human Button' Peter Hennessy also meets the submariners who work with Britain's nuclear weapons today.
This programme was first broadcast at 2000 GMT on Tuesday, 2 December 2008 on BBC Radio 4.
Music: 'In An Empty Space In An Empty Space' composed by Oliver Vessey. Slideshow production by Paul Kerley. Publication date 1 December 2008.
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