In case of nuclear disaster: stay calm and carry on…living underground.

In 1956, the British government began building a sprawling subterranean city two hours from London underneath the ancient, 13,000-person town of Corsham. If the nation was struck with a nuclear bomb, 4,000 government employees would be shuttled via a secret train line from downtown London to a blast-and-radiation-proof bunker code-named “Burlington”. From these emergency government war headquarters, as they were designated, Britain could resume governing while the world above burned.

The secret word for this evacuation was “orangeade,” a 1962 copy of the Cabinet Office’s War Book revealed in 2011. The code would also be told to security agents guarding the site. "Advance parties going to Burlington would be kept to a minimum and every effort would be made to maintain the cover story,” the document explained. From Burlington, the assorted agencies could plan their next moves. “The chiefs of staff will be ready to make recommendations on the use of the nuclear retaliatory forces based in the UK."