What Blair must do if he is to win back our trust

After months of brittle refusal to bend to reality, the softening-up exercise is in full swing. Last week the Prime Minister appeared before a dignified committee of MPs to admit what the whole country has known for over a year - that Saddam Hussein did not have weapons of mass destruction. Yesterday an anonymous sympathiser painted a touching picture of a tortured Tony Blair going through a "long night of the soul" about whether to carry on - and concluding that, on balance, he should.

After months of brittle refusal to bend to reality, the softening-up exercise is in full swing. Last week the Prime Minister appeared before a dignified committee of MPs to admit what the whole country has known for over a year - that Saddam Hussein did not have weapons of mass destruction. Yesterday an anonymous sympathiser painted a touching picture of a tortured Tony Blair going through a "long night of the soul" about whether to carry on - and concluding that, on balance, he should.

The last part of the No 10 strategy for handling the Butler report, to be published on Wednesday, is potentially the most cynical. The Prime Minister's advisers are discussing the precise terms of what they are apparently calling his "non-apology apology" for the flaws in the case for war. This has been on the stocks for some time. It was under discussion at the time of the Hutton report in January, but had to be shelved because the judge was so unexpectedly categorical in his exoneration of the Government.

Lord Hutton, however, is a judge, accustomed to coming down on one side or the other of a dispute - in that case over flawed reporting by the BBC. Lord Butler, on the other hand, is a former civil servant. He is an establishment figure to be sure, but he will not want to be seen as partisan, and the subject of his inquiry goes to the heart of the Prime Minister's case for war.

It will be difficult for Lord Butler and his colleagues to avoid conclusions that are more damaging for Mr Blair than those of the Senate Intelligence Committee last week were for George Bush.

Weapons of mass destruction were always more important to the British case for war than they were for the American. The Bush administration had developed a policy of "regime change" that was independent of the existence of illegal weapons programmes. President Bush and Donald Rumsfeld did not even pretend to care very much about international law. Furthermore, the Prime Minister's office was involved in the presentation of intelligence information to a greater extent than was the White House - although the Senate committee was limited by its partisan nature in what it could say about the pressure on the Central Intelligence Agency from the President's staff.

On Wednesday, it will no longer be possible for the Prime Minister to pretend that the intelligence on which his case for war rested was sound. This paper has three simple tests to measure Mr Blair's response.

First, he has to accept that he made mistakes. We do not expect him to admit that the war was unjustified. To use his curiously grudging expression, we "do not disrespect" his belief that Saddam was a vile dictator and a proven regional troublemaker and that it was reasonable to suppose that Iraq would be a happier place and the world safer without him. But he cannot expect to regain credibility unless he says that he made a mistake in not questioning the intelligence more rigorously; another in being so closely involved in presenting the intelligence; and a third in relying so heavily on patently unreliable claims, such as the infamous 45 minutes.

Second, heads must roll. This was a catastrophic and near-total intelligence failure. It beggars belief that John Scarlett, who took full, personal responsibility for the dossier on Iraq's WMD as chairman of the Joint Intelligence Committee, should avoid the consequences of any adverse finding. He cannot be allowed to deploy what is known as the Westwood defence, after the chief constable of Humberside, who argued, when he was criticised by the Soham inquiry, that he had got his force into the mess and was therefore the best person to get them out of it. If George Tenet, the director of the CIA, and another senior official have resigned, then so must Scarlett and possibly others.

Third, the Prime Minister must show that he and the Government have learnt from the failure by announcing explicitly that policy has changed. Had he known then what he knows now, he should say, he would have made a different case for deposing Saddam. He must acknowledge that Britain will never again join in a pre-emptive attack on the basis of intelligence alone.

If the Prime Minister fails any of these tests, then the trust in him of the British people will continue to corrode, weakening not just his position but Britain's standing in the world.