How judge was misinformed about Iraq's WMD threat

In Autumn 2002 the dossier on Iraq's weapons of mass destruction - the clinching argument which Tony Blair believed would swing a deeply sceptical public behind the war - was just weeks away. There had been draft after draft, with copious suggestions on "presentation" from Downing Street.

In Autumn 2002 the dossier on Iraq's weapons of mass destruction - the clinching argument which Tony Blair believed would swing a deeply sceptical public behind the war - was just weeks away. There had been draft after draft, with copious suggestions on "presentation" from Downing Street.

But there was one serious worry nagging away at MI6. There was a lack of hard evidence that Iraq had an active chemical and biological weapons programme.

One source, believed to be a high-ranking Baath party member, had supplied some information about such a capability. But it was, he readily admitted, chatter he had picked up from his "high-level" contacts in Baghdad, and thus hearsay.

Then came the break. An Iraqi source, not an exile who was full of fanciful tales, but a general who sat at Saddam Hussein's table, came forward with claims of an ongoing chemical and biological programme.

What is more, the man, although new as an agent, had already supplied information, albeit of much lower value, which was deemed to be credible.

However, the informant had revealed that he was getting his material about chemical and biological weapons from another man, and this man had links with the exile groups that MI6 had been so cautious about. The case officer duly noted the problem, and Lord Butler acknowledged that a caveat had been included in the intelligence docket.

This new information underpinned another sensational allegation that Iraq could launch chemical and biological weapons hitting British bases in Cyprus within 45 minutes of an order to deploy them.

Such was the sense of excitement within MI6 that Sir Richard Dearlove, the head of the service, personally visited Downing Street to tell the Prime Minister and Sir David Manning, his foreign affairs adviser, about the new source. This visit was a break from protocol. The intelligence should have been channelled through the Joint Intelligence Committee. Sir Richard told Mr Blair and Sir David that the new source was "potentially important" but also pointed out that he "remained unproven ... on trial".

Twelve days after the meeting, the Iraq weapons dossier was published and Mr Blair declared in the foreword that the document was "extensive, detailed and authoritative", and declared that intelligence had "established beyond doubt" that the Iraqi regime was continuing to produce WMD.

That is where it rested until MI6 agents went out to Iraq after the fall of Baghdad. From the end of April onwards they interrogated prisoners and interviewed their informants. They tracked down and spoke to the man said to have supplied Sir Richard's prize source with the chemical and biological programmes details. He flatly denied saying any such thing.

This was passed on to MI6 in London by the end of June last year. By the second week of July, it is believed, MI6 had informed the JIC, chaired by John Scarlett, that it was withdrawing that intelligence. The normal practice is that all those who had received the original intelligence, now proved to be untrustworthy, should be informed at the earliest opportunity. This included the Prime Minister.

The Hutton inquiry began on 11 August. Giving evidence, the Prime Minister, Mr Scarlett and Sir Richard all failed to mention the withdrawal of intelligence and saidagents in Iraq were believed to be reliable.

Yesterday, Downing Street insisted that the first time Mr Blair knew about the discredited intelligence was when he saw the Butler report. And the reason Mr Scarlett had not mentioned it, giving evidence two months after MI6 had withdrawn the intelligence, was that "the validation process was still ongoing".