The letters of last resort are four hand-written letters by the Prime Minister of the United Kingdom that contain orders to the commanders of the four British ballistic missile submarines on what to do in the case that an enemy nuclear strike has destroyed the UK and killed the Prime Minister.
The letters are stored inside two safes in the control room of each submarine.[1] These notes instruct the captain of what action to take in the event of the United Kingdom being attacked with nuclear weapons that destroy Her Majesty's British Government and/or the chain of command.
Although the final orders of the Prime Minister are at his or her discretion, and no fixed options exist, four known options are often presented to prime ministers by military advisers when writing such notes of last resort: (i) Captain ordered to respond to the nuclear attack on the UK by launching submarine's nuclear weapons; (ii) Captain ordered not to respond with nuclear weapons; (iii) Captain ordered to use own judgement whether to return fire with nuclear weapons; (iv) Captain ordered to place himself and ship under the command of Her Majesty's Government of Australia, or alternatively of the President of the United States. This system of issuing notes containing orders in the event of the head of government's death is said to be unique to the United Kingdom (although the concept of written last orders, particularly of a ship's captain, is a naval tradition), with other nuclear powers using different procedures. Such orders are destroyed unopened whenever a prime minister leaves office, so the decision of its use or not by previous prime ministers are known only to them - however, all relevant former prime ministers have supported an "independent nuclear deterrent", as does incumbent David Cameron.[2]
Only former prime minister Lord Callaghan has given any insight on his orders: Callaghan stated that, although in a situation where nuclear weapon use was required - and thus the whole purpose and value of the weapon as a deterrent had failed - he would have ordered use of nuclear weapons, if needed: ...if we had got to that point, where it was, I felt it was necessary to do it, then I would have done it (used the weapon)...but if I had lived after pressing that button, I could have never forgiven myself[3]
According to Peter Hennessy's book Secret State: Whitehall and the cold war 1945 to 1970, the process by which a Trident submarine would determine if the British government continues to function includes, amongst other checks, establishing whether BBC Radio 4 continues broadcasting.
