An eerie reminder of the Cold War, the protected headquarters of the Royal Observer Corps No.20 Group are sunk several metres below the ground on the outskirts of York. Here up to 60 scientists and trained civilians worked in preparation against nuclear attack. An open secret, the very existence of the bunker would have warned the Soviet Union of Britain's preparedness to withstand attack and to seal off its workforce from a potentially contaminated outside world. This new guide contains a tour and history of a site which evokes a chilling period of recent history.