For the third time in four years, Britain appears on the brink of a prime minister announcing their plan to leave office - not because they lost an election, but because their own party decided they'd rather have someone else. Sir Keir Starmer, less than two years after winning a general election, is expected to set a timetable for his departure, possibly as early as this morning.

This ritual has become depressingly familiar. In July 2022, Boris Johnson stood in Downing Street and reluctantly admitted his MPs were fed up. Three months later, Liz Truss did the same. Now it's Starmer's turn, after a premiership that many on his own side describe as 'deflating' for months. He tried to raise the bar for successors, blocking Andy Burnham's first attempt to return to Westminster and insisting he'd fight any leadership challenge. But Burnham's decisive by-election victory last week uncorked the bottled-up dissent.

At least four cabinet ministers, including the home and foreign secretaries, have told Starmer to set a departure date. He has two options: sack them and stumble on while his likely successor barrels toward Westminster, or seize what agency remains and shape his exit. The party debates whether to have a full contest or a quick coronation - Burnham could be PM within a week or two if momentum is overwhelming.