For Elizabeth II, the plan for what happens next is known as “London Bridge.” The prime minister will be woken, if she is not already awake, and civil servants will say “London Bridge is down” on secure lines.

The last time a British monarch died, 65 years ago, the demise of George VI was conveyed in a code word, “Hyde Park Corner”, to Buckingham Palace, to prevent switchboard operators from finding out. The first official to deal with the news will be Sir Christopher Geidt, the Queen’s private secretary, a former diplomat who was given a second knighthood in 2014, in part for planning her succession. Her eyes will be closed and Charles will be king. Not long afterwards, Dawson injected the king with 750mg of morphine and a gram of cocaine – enough to kill him twice over – in order to ease the monarch’s suffering, and to have him expire in time for the printing presses of the Times, which rolled at midnight. “The King’s life is moving peacefully towards its close,” was the final notice issued by George V’s doctor, Lord Dawson, at 9.30pm on the night of 20 January 1936. “The Queen is suffering from great physical prostration, accompanied by symptoms which cause much anxiety,” announced Sir James Reid, Queen Victoria’s physician, two days before her death in 1901. There will be bulletins from the palace – not many, but enough. A nation’s life becomes a person’s, and then the string must break.

The bond between sovereign and subjects is a strange and mostly unknowable thing. He will look after his patient, control access to her room and consider what information should be made public. In these last hours, the Queen’s senior doctor, a gastroenterologist named Professor Huw Thomas, will be in charge.

When the Queen Mother passed away on the afternoon of Easter Saturday, in 2002, at the Royal Lodge in Windsor, she had time to telephone friends to say goodbye, and to give away some of her horses. I n the plans that exist for the death of the Queen – and there are many versions, held by Buckingham Palace, the government and the BBC – most envisage that she will die after a short illness.

7 days to die drawbridge dimensions