On the day of the Brown fightback we learn of the arcane rules of the Labour party which make challenging a Labour PM very difficult. No-one persuaded Mr Purnell, who clearly thinks that if he and others like him keep on walking out, the momentum will become unstoppable.
The Chancellor seems to have worked out that he can make the sack more difficult to administer if he refuses in advance any other job. The rebels have now staked out some of their positions. Do they have the numbers to make it work?