Gordon Brown's critics inside the Labour party believe there is only one person who can force him into a serious contest for the leadership. That person is David Miliband, the 40-year-old environment secretary.

If Mr Miliband decided to run, a string of cabinet figures would probably back him. John Reid, the home secretary and John Hutton, the work and pensions secretary, would probably offer their support. Up to 10 cabinet ministers might do the same. Many Labour MPs, who have long taken the view that the future is Gordon Brown, would suddenly have to think very hard about their allegiance.