Leading article: Close Guantanamo now

There is something slightly unreal about the Prime Minister's inexhaustible ability to put on a brave face. The looting in Baghdad broke out in earnest on the day the statue of Saddam Hussein was pulled down, and the disorder in Iraq has grown worse ever since. Now, sectarian civil war is raging in four provinces, which include the main population centre of the capital. Yet last week, Tony Blair flew into Baghdad International airport, and then to the Green Zone by means of a corkscrewing helicopter, putting out chaff to decoy the rocket-propelled grenades. For the fifth time. As he did every time before, he hailed a turning point. Elections, a referendum, a largely symbolic hand-over of sovereignty to the Iraqis: this time it was the formation of a national unity government. Mr Blair's optimism is beginning to look like desperation at some distance from reality.

Which is unfortunate, because it undermines the credibility of his message, much of which is right - despite his responsibility for turning Iraq into a charnel house in the first place. British and American forces do have a duty to stay in Iraq. This is not because the violence there is a struggle between terrorism and democracy - that is much too simple. The supposed defenders of democracy have been guilty of human rights abuses, and the allegation that Marines deliberately shot Iraqi civilians is only the latest of a long line of charges against US and British forces. Mr Blair's simplistic picture of Iraq overlooks, too, the extent to which the presence of foreign troops inflames Iraqi nationalism, albeit of a Sunni-tinged variety. Yet British and US troops must stay because the consequences of withdrawal are still worse. Meanwhile, as Malcolm Rifkind argues on page 31, President George Bush and Mr Blair must keep an open mind on the need for a more federal Iraqi state, if that is the only way to accommodate Sunni resentment of Shia domination.

Mr Blair's brave face was on display in Washington too, at his joint news conference on Thursday with Mr Bush. In contrast to previous appearances, they adopted a slightly humbler tone, and looked like two leaders trying to salvage some shred of honour from a policy that has gone seriously wrong. They admitted that mistakes had been made in Iraq, and Mr Bush accepted that some of the rhetoric of the wider "war on terror" had been misplaced, such as saying that Osama bin Laden was wanted "dead or alive".

Yet they failed to ask for several other offences to be taken into consideration. Our report today that 14- and 15-year-olds have been held at Guantanamo Bay is a further reminder of how the stateless prison camp on a US base in Cuba is, in the British Attorney General's words, a "symbol of injustice". Eventually, the US Supreme Court is bound to rule that Guantanamo is unconstitutional. No future president is ever likely to repeat such an experiment in suspending US and international law.

But Guantanamo is a mistake that Mr Bush could actually do something about, as opposed to past words misused, or the invasion of Iraq, or the failure to send enough troops to police the place. If the Prime Minister is worried about his legacy, he should have told the President that if he really wanted to salvage something from the wreckage, he would close Guantanamo now.