Letters of last resort

The letters of last resort are four identically worded handwritten letters from the prime minister of the United Kingdom to the commanding officers of the four British ballistic missile submarines and stored on board of each.^[A] Born out of Britain's unique vulnerability to the effects of nuclear attack,^[2] the letters contain orders on what action to take if an enemy nuclear strike has both destroyed the British government and has also killed or otherwise incapacitated both the prime minister and their designated "second person" of responsibility, typically a high-ranking member of the Cabinet such as the deputy prime minister or the first secretary of state. If the orders are carried out, the action taken could be the last official act of His Majesty's Government.^[3]

HMS Vigilant, one of four Vanguard-class submarines comprising the UK's nuclear deterrent.

If the letters are not used during the term of the prime minister who wrote them, they are destroyed unopened after that person leaves office, so that their content remains unknown to anyone except the issuer.^[4]

Process

A new prime minister writes a set of letters after taking office and being told by the Chief of the Defence Staff "precisely what damage a Trident missile could cause".^[5] The documents are then delivered to the submarines in sealed envelopes, and the previous prime minister's letters are destroyed without being opened.^[6] The letters do not have to be written immediately after the briefing on Trident's capabilities, and in any case the previous prime minister's set of letters remains in effect until the new letters have been delivered to each submarine.^[7] Letters aboard Polaris submarines were accompanied by a separate letter from the Commander-in-Chief Fleet which was to be opened first as it contained the conditions for opening the prime minister's letter;^[8] no such letter from the Commander-in-Chief Fleet (later Fleet Commander) has been referred to in accounts of the last resort procedure for Vanguard-class submarines.

In the event of the deaths of both the prime minister and the designated alternative decision-maker as a result of a nuclear strike, the commander(s) of any nuclear submarine(s) on patrol at the time would use a series of checks to ascertain whether the letters of last resort must be opened.^[2] In 1983, the procedure for Polaris submarine commanders was to open the Commander-in-Chief Fleet's letter if there had been an evident nuclear attack on the United Kingdom or if British naval communications had ceased for four hours.^[8] It has been reported that the process by which a Vanguard submarine commander would determine the continued existence of the British government involves the monitoring of a variety of communication signals,^[7] with the ability or inability to receive a BBC Radio 4 broadcast having particular significance.^[9][10]

Options

While the contents of the letters are secret, there are four "basic" options given to the prime minister for inclusion. The prime minister might instruct the submarine commander to:^[11][7]

1. retaliate;
2. not retaliate;
3. use their own judgement; or,
4. place the submarine under an allied country's command if possible. Australia and the United States have been mentioned in the context of this particular option.^[12]

The Guardian reported in 2016 that the options are said to include: "Put yourself under the command of the United States, if it is still there", "Go to Australia", "Retaliate", or "Use your own judgement".^[5] The actual option chosen remains known only to the writer of the letter.

Fiction

David Greig's 2012 play The Letter of Last Resort deals with the consequences and paradoxes of the letters.^[13] The play was first staged in February 2012 as a part of a cycle of plays on "The Bomb" at the Tricycle Theatre in London, directed by Nicolas Kent, with Belinda Lang playing the role of the incoming prime minister and Simon Chandler, her advisor.^[14] The production was also seen at the Traverse Theatre in Edinburgh, for the Edinburgh Fringe later the same year.^[15] The following year it was broadcast on BBC Radio 4, with the same cast, first transmitted on 1 June 2013.^[16]

The KGB's attempts to obtain the contents of the letters of last resort are part of the plot of the BBC Cold War spy drama The Game (2014).^[17]

See also

• Dead Hand
• Dead man's switch
• Fail-deadly
• Mutual assured destruction
• Nuclear weapons and the United Kingdom § Nuclear weapons control
• Operation Looking Glass
• Samson Option
• Trident nuclear programme
• Nuclear football
• Cheget

Footnotes

1. The United Kingdom relies on four Vanguard-class submarines to provide its nuclear deterrent. At least one submarine is always armed and on active service, carrying up to 16 Trident II submarine-launched ballistic missiles. Each missile has a range of 7,000 miles (11,000 km), and can carry 12 independently controlled warheads each capable of destroying a large city.^[1]