There is nothing new about Tony Blair's departure. Most prime ministers have to be dragged out of 10 Downing Street kicking, screaming and hanging on to the door. The job is a drug. "No one ever comes out of No 10 completely sane," the Tory whips used to say as they watched the grisly dying days of Margaret Thatcher's premiership.
Of the 20th century's 20 premiers, only three gave the job up voluntarily. Robert Cecil, Lord Salisbury, resigned in 1902 at the age of 72, in such good odour with his party that he was able to bequeath the premiership to his nephew Arthur Balfour. You are PM, they told Balfour, because "Bob's your uncle", and the phrase stuck.
Stanley Baldwin went peacefully in 1937, when he was 69. Having delayed his retirement to sort out the abdication crisis, there seemed nothing else around which was too important to be left to Neville Chamberlain.
In 1976 Harold Wilson calmly announced that at 60 it was time to retire. Wilson could not resist a last undignified twitch of the power he was giving up - the infamous Lavender List of those he wished to ennoble. "Such a graceful exit, and then he had to do this on the doorstep," said one of his friends.
The grisliest departures are of those forced out by their colleagues while still in the job. In 1916 a plot took several weeks to force out Herbert Asquith and split the Liberals so decisively that they have never again formed a government. It was done partly by inspired press leaks, mostly to the Times, which carried full accounts of bad-tempered meetings between Asquith and Lloyd George. Gordon Brown, who knows his history, is said to be terrified of being the Labour equivalent.
The next grisly case was Chamberlain's in 1940. His chief whip, David Margesson, did what chief whips do, and tried to bully his MPs into toeing the line. The young John Profumo was one of 33 Tory MPs who rebelled in the crucial debate, and Margesson, after shouting at him for several minutes, concluded: "I can tell you this, you utterly contemptible little shit. On every morning that you wake up for the rest of your life, you will be ashamed of what you did last night."
The grisliest of the lot, until now, was Thatcher. She said she would go "on and on," but this was as unsettling as was Blair's undertaking to do the opposite. She twitched on the end of the rope for ages. Her fight for her legacy destroyed her party, and it is only now, more than a decade later, starting to recover. That precedent, too, has not escaped Brown's attention.
Francis Beckett is editor of the series "Prime Ministers of the 20th Century", published by Haus Publishing