Leading article: The exit dilemma

At least the Prime Minister understood one thing. When the 15 British hostages returned from Tehran, he realised that the death of four of their comrades in arms in Basra earlier that morning was more important. Plainly, we should be grateful for the safe return of the sailors and marines, and we should note the lesson for the future that negotiation rather than sabre-rattling is the way to get results from Iran.

But the real significance of the hostage crisis is that it dramatises the extent to which British forces are being sucked into a regional conflict being played out in Iraq. It is a conflict in which Iran is playing an unpredictable and destabilising role. We have no way of knowing - and nor does Mr Blair, obviously - whether or not Iran was implicated in the attack that killed the four young soldiers in Basra. It is all too plausible that elements of the Iranian regime are financing and arming Shia militias in Iraq. But the implication of Mr Blair's finger-pointing is ominous. It is that he may be about to argue that the gradual withdrawal of British forces from southern Iraq should be postponed - and for a very long time - in order to counter the threat of Iranian interference. This could be to compound the original mistake, of getting into a regional Sunni-Shia conflict in which Western forces act as an incendiary catalyst.

The deaths of the four British soldiers seem painfully sad. Once a decision has been taken to start to withdraw forces from a theatre, it becomes increasingly difficult to answer the question: what are our soldiers dying for? That is why the Prime Minister is so adamant that no such decision has been taken, and that the "drawdown" will be determined by circumstances on the ground. And it is why he insists in every tribute to the fallen that they died doing an "essential" job. But General Sir Richard Dannatt, the head of the Army, blew the gaffe on that last autumn, by admitting that the presence of British forces in Iraq was making the security situation worse.

With the arguments for and against British withdrawal finely balanced, it becomes increasingly difficult to maintain the domestic support for the mission that is necessary if lives are going to continue to be risked. The consequences of pulling out look bleak, but so do those of staying. It is not a happy legacy for Mr Blair to leave.

Interesting? Click here to explore further