The letters of last resort are the letters written by the UK Prime Minister to the naval officers in command of the four nuclear submarines which provide the UK's nuclear deterrent, containing instructions in case of the destruction of the government & the incapacitation of the PM. They are written as soon as possible after there is a change of Prime Minister, and the previous letters are said to be destroyed without being opened.

What is known about the process behind the creation of the letters? Has any Prime Minister or insider ever revealed their contents? Does the PM have to pick from a list of options, as this Guardian article implies, or can the PM write whatever he/she sees fit?

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    I don't know how the system actually works in the UK but it seems odd to me to force every PM to rewrite these letters from scratch. Showing the new PM the existing versions and asking whether any update/ change is needed seems a lot more sensible.
    – quarague
    Feb 26, 2020 at 10:43
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    @quarague That could be tricky logistically. Apparently, the original envelopes are each in a safe on a submarine. There are no copies, and no-one sees them except the PM. The old ones are destroyed only when a new one arrives to replace it. Feb 26, 2020 at 14:29
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    @SteveMelnikoff Maybe the system is designed that way but this would mean that the content could switch from 'destroy Moscov' to 'don't bother, all is lost anyway' to 'destroy Washington' depending on how the current PM feels about geopolitics. That doesn't seem like a good way to sensibly define what to do as a last resort.
    – quarague
    Feb 26, 2020 at 15:08
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    @SteveMelnikoff that seems not that plausible - I mean, governments can and will change while the submarine is at sea, and it should be possible to inform the appropriate new officials what the actual currently standing orders to the submarines are instead of saying "who knows, they're going to do something".
    – Peteris
    Feb 26, 2020 at 21:34
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    @quarague These letters only exist for when the UK's totally destroyed by nuclear fire though. e.g. no government, no military command, and no BBC radio 4. It's meant to be the last order that sub gets, since it's all it can really do at that point.
    – bobsburner
    Feb 27, 2020 at 9:21

1 Answer 1


Not formally.

From the Wikipedia article on the letters of last resort:

The letters are written as soon as a new prime minister takes office, after they have been told by the Chief of the Defence Staff "precisely what damage a Trident missile could cause". These are then delivered to the submarines, with the previous prime minister's letters being destroyed without being opened.

(emphasis mine)

The Wikipedia article cites this one:

David Cameron's letters, which were written when he took office, will be burned without being opened.

Unless he decides to tell us, we will never know what his decision was.

It however goes on to say that there has been someone who revealed their decision:

Only one Prime Minister has revealed that secret.

James Callaghan told the historian Peter Hennessy: "If we had got to that point, where it was, I felt, necessary to do it, then I would have done it.

"I've had terrible doubts, of course, about this.

"I say to you, if I had lived after having pressed that button, I could never ever have forgiven myself."

We don't, however, know what was actually written in the letter - only what the decision was.

  • I'm not sure if the last quote really relates to the letters of last resort - he refers to pressing a button and not being able to forgive himself afterwards; the letters of last resort only come into play after the PM's assumed death in a nuclear attack on the UK.
    – CDJB
    Feb 27, 2020 at 10:10
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    @CDJB in the context of the source, I'm taking that last quote to mean that James Callaghan ordered the submarine captain to retaliate. He would not be directly pressing the button, but by ordering it, he is indirectly doing so. And he might not be dead - the process needed to verify if the PM is dead is probably not foolproof.
    – Allure
    Mar 5, 2020 at 10:20

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