Command options for PMs’ apocalypse letters to nuke sub captains not held in MOD documents
The Ministry of Defence (MOD) does not hold information on what options Prime Ministers’ face when writing their letters to the captains of nuclear-armed submarines - which contain the instructions on what to do if communications with the chain of command are cut off.
The MOD’s lack of information on the letters was revealed in response to a request made under the Freedom of Information (FOI) Act by 20 Working Days.
Attention was drawn back to the existence of the so-called ‘letters of last resort’ because of the UK getting its sixth Prime Minister in 10 years, as Andy Burnham replaced Keir Starmer as leader of the Labour Party.
It is widely understood that one of the first tasks a Prime Minister has on walking through the door to Number 10 Downing Street is writing the letters to the submarine captains.
The letters are written so that, if communications are not possible between the submarine and the wider military and political command and control structure, the submarine captains are able to find out what they should do by reading the pre-written letters which are believed to be sealed until they are needed.
The classic hypothetical scenario involves nuclear war breaking out, London and other military and political headquarters being destroyed or otherwise compromised, and nuclear submarines remaining operational but without a command structure telling their captains what to do.
The existence of the letters was confirmed by the MOD in an internal review of a FOI request in 2015. The results of the internal review were addressed to a Mr D Black.
The internal review found that the MOD's decision to neither confirm nor deny whether the information Black had requested relating to the letters of last resort was an "overly-cautious" approach to take, and instead should release certain information about the letters.
It said: “Under section 1 of the Act I can confirm that obsolete letters are not held. I have been advised that this is because the letters are only retained until replaced by a later version.”
One department no longer holding the letters does not necessarily mean that the government as a whole has no record of the contents of the letters.
In 2016, just before Theresa May took over the role from David Cameron, the Guardian reported: “The options are said to include the orders “Put yourself under the command of the US, if it is still there”; “Go to Australia”; “Retaliate”; or “Use your own judgment”.”
On 4 July 2026, using the FOI Act, 20 Working Days asked the MOD to share “any documents you have which show whether the MOD plan to release historic Letters of last resort, possibly to the National Archives or whether they might be made available under the FOI Act in future?” This was with reference to the 2015 FOI.
The request also asked for “any documents which show whether the options include the orders ‘Put yourself under the command of the US, if it is still there’; ‘Go to Australia’; ‘Retaliate’; or ‘Use your own judgment’,” as per the reporting in the Guardian.
In response, on 16 July, the MOD said: “We have treated your correspondence as a request for information under the Freedom of Information Act 2000 (the Act). A search has been completed within the Ministry of Defence (MOD) and we can confirm that the MOD holds no information in scope of your request.
“Under section 16, whereby the public authority should provide advice and assistance, so far as it is reasonable to do so, you may find it helpful to note that the response to FOI2015/086381, which you referred to in your email, confirmed that the MOD did not hold versions of the so called ‘letters of last resort’ issued by previous Prime Ministers and that letters currently onboard the submarines are not retained once they are superseded by new versions.”
FOI2015/086381 is the 2015 request made by Mr D Black.
The MOD continued: “Further, as the letters are written by the Prime Minister of the day, they are administered by the Cabinet Office. In response to a 2015 request for letters written by previous Prime Ministers, the Cabinet Office stated that the information is not held.
“These previous responses, taken together, suggest that historic letters are not retained and therefore cannot be released in future to either The National Archives or to individuals in response to requests under the Act.
“As the letters are administered by the Cabinet Office, you may wish to approach them regarding the second part of your request relating to what options the letters might contain.”
20 Working Days has submitted the same two requests to the Cabinet Office under the FOI Act following the recommendation by the MOD.
The MOD was approached for comment.