Tony Blair's defeat over the 90-day detention plans has killed two long-lasting Westminster myths: that Labour MPs are supine and that, however much they were prepared to rebel when the government had a large majority, they would behave themselves once the going was tougher. As if to prove that ignorance deplores a vacuum, along comes another wannabe myth to take their place: that the Prime Minister has got into trouble with his backbenchers because he has already pre-announced his resignation.
The opposite is true. Even if it has weakened his authority elsewhere, his impending retirement helped him in this particular vote. Nor is it the source of his difficulties with any impending legislation. If you doubt this, imagine that there had been no announcement and that the entire Parliamentary Labour Party thought he intended to fight the next election. In such an alternative universe, the MPs who want to see him removed - especially those who would like to replace him with Gordon Brown - have the perfect reason to put the boot in.
But back in the real world, there were very few Brownite rebels in the vote on 9 November. Most of those voting against Blair might want him to go sooner rather than later, but they do not want to see him brought down in a torrent of defeats. What they want is what they were promised: a dignified and orderly handover of power. For the most part, they are willing to compromise with the government to avoid a defeat. It was not obduracy on the part of backbenchers that was responsible for the mess.
That was one of the reasons why, having returned from Israel, Gordon Brown was unable to dissuade many of the MPs who were intending to rebel. Those who saw the events as a Brownite plot are misguided. Leave aside that inheriting a party which has got used to defeating its leader is hardly in Brown's interests, all such discussions exaggerate the extent to which the Brownite/Blairite divide extends within the PLP. No matter how you measure it, the majority of Labour politicians are neither Brownite nor Blairite.
The myth suits both camps. It allows those around Brown to pretend they control swatches of troops, ordered to attack or retreat at will. Similarly, it allows Blairites to blame the Brownites for scheming. The truth is more prosaic. When Blair has got himself into difficulties with the PLP, as he did over the Terrorism Bill, it has not been because of Brown, but because he has managed to alienate the broad non-aligned mainstream on his back benches. When Prime Minister Brown runs into trouble with the PLP - as he will - it will be for the same reason.
What happened was exactly what the whips had been worried about four years ago. Shortly after the 2001 election the assumption within the government was that its then-large majority would ensure it could make it through the parliament without being defeated. It therefore attempted an ambitious longer-term strategy: to look ahead to Labour's third term. The goal of the second term was to be to nurture good relationships with backbenchers and to prevent the habit of rebellion from becoming too widespread, so that if Labour won a third term - with what the government (rightly) assumed would be a reduced majority - the whips would have credit in the bank with Labour backbenchers, which they could then use to get legislation through, even with that smaller majority.
Asked just before May's election whether he thought that strategy had been a success, one whip laughed and replied: "I'm not sure it worked." Instead of constraining it, the events of the 2001 parliament - notably, but not exclusively, Iraq, top-up fees and foundation hospitals - made back-bench rebellion a relatively commonplace activity, and one that few backbenchers had not taken part in at some point. By the end of the last parliament what one whip called "the threshold of rebellion" had been crossed by most Labour MPs. Rebelling had become a habit and, as with most habits, it will be hard to break.
Philip Cowleyis author of The Rebels: how Blair mislaid his majority, just published by Politico's