Letters of last resort: PM’s early task to write to UK’s nuclear sub commanders

Royal Navy security personnel stand guard on HMS Vigilant at its Clyde naval base in 2016. At least one of the UK’s four nuclear submarines must be on patrol at all times Photograph: Jeff J Mitchell/Getty Images

It is “the moment when they know what being prime minister is all about”, according to Whitehall historian Lord Hennessy.

One of Liz Truss’s early tasks will be to write instructions by hand to each of Britain’s four nuclear submarine commanders, directing them how to respond in the event of an all-out attack that will have killed her and destroyed the UK. They are known as the letters of last resort.