U.K. Briefly Had Ability to Fire U.S. Nuclear Missiles During Cold War

At one point during the Cold War, a mechanical misstep ended up giving the United Kingdom the ability to unilaterally launch U.S. nuclear-armed missiles based on its territory, the London Telegraph reported on Thursday.

From 1958 to 1963, the United States based Thor intermediate-range ballistic missiles in the United Kingdom. The two allies agreed to a dual key system that gave the Royal Air Force the ability to turn on the missile and the U.S. Air Force the power to arm the warhead. The framework was intended to ensure that both nations were in agreement on the decision to fire any IRBMs.

However, some of the locks got mixed up.

"An RAF technician discovered during routine servicing of an inert missile that a British key turned the U.S. Air Force lock. A comprehensive check of the other missiles revealed that this was also the case for one other USAF lock. All the locks were changed as a result," reads a summary of the incident written years after the fact in 1983 by former U.K. Prime Minister Margaret Thatcher. The document was published this week by the National Archives.

It was official British policy in the 1980s that in the event the country came under a catastrophic attack that incapacitated the prime minister, as many as three high-ranking ministers that had previously been chosen as "nuclear deputies" would be empowered to decide how to use the nation's nuclear weapons, the Telegraph separately reported, citing another recently declassified government document.

"If London were destroyed, the senior surviving minister would take over the surviving central government, and arrangements have been made for him to exercise control of the Polaris [nuclear submarine] force at sea if neither you nor one of the nuclear deputies survived," reads one briefing paper. The document was prepared by the Thatcher administration and would have  been given to the new prime minister had the Conservative Party not won the 1983 general election.