The Sketch: Unconvincingly, he slalomed from certainty to evasion

At the bottom of all this is the fact that Alastair Campbell is just too attractive for the country's good. The overwhelming charm of the alpha male has allowed him to walk down Whitehall with a palm tree in his fist telling anyone he likes what to do, and they do it - ministers, the Prime Minister, civil servants of every sort.

It's an astonishing achievement of Mr Campbell's, considering one of the primary purposes of the British constitution over the past thousand years has been to prevent men like him doing things like that.

Thus, in his capacity as a special adviser, he can tell a very senior civil servant, the head of the Joint Intelligence Committee, to change the wording of a central claim from a subjunctive mood to an indicative. A bit of grammar shows that Mr Campbell's change produces a new intelligence claim.

What was a possibility is now an actuality. And as a result, the country goes to war with Iraq.

As we know, Alastair Campbell isn't an intelligence expert but has leached himself into intelligence. The process isn't one way. John Scarlett is no expert in presentation but has allowed Alastair Campbell to leach into his mind. It is a very bad sign. It has turned him from an icon of respectability into an unreliable witness.

As he is being tipped to be the next head of MI6 and he has a panoply of lawyers examining reports like this, let us look at the evidence he gave yesterday.

Lord Hutton's counsel asked him: was there any view among his colleagues or himself that No 10 was trying to beef up the dossier? What an extraordinary answer he gave, replying firmly: "None at all." We wondered in what way No 10's efforts could be interpreted as not beefing up the dossier? All Mr Scarlett's own evidence concerning the joint drafting, the online contact with No 10, the constant meetings, the changes requested by Mr Campbell and agreed to by Mr Scarlett himself contradicted this.

There were other occasions where the JIC head belied himself. Dame Pauline Neville-Jones' well-publicised opinion was referred to. "There was clearly some turbulence in the machine," she had said. Was that fair, Mr Scarlett was asked? "I should say she was completely wrong. Or wrong. It depends what you mean by turbulence," Mr Scarlett said in a rush, slaloming from certainty to evasion.

Then, later, he told the courtroom: "I was not aware of any unhappiness about the contents of the dossier." In which case, his intelligence contacts weren't as good as the media's. That can't be a good thing in an intelligence head, not one aspiring to lead MI6.

He was also asked about the Foreign Affairs Committee verdict that the dossier's language was more assertive than traditionally used in intelligence documents. Was that fair? "No," he said, "it's wrong." But it isn't wrong, manifestly.

And finally, Mr Scarlett offered us a prepared statement so outrageously unreliable it can only have been drafted in the Prime Minister's office.

What was the purpose of the dossier? It was to put into the public domain the intelligence assessment which was being provided to the Government. "It was absolutely not a document designed to make a case for anything," he said.

We can't believe that, even if we try. Not without half a pint of sodium pentathol. All that strengthening the evidence, all that tightening of the language, all that recasting and rewriting - the purpose of it can only be to make the case for war.

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