The Attorney General's doubts about the legality of the Iraq war were finally laid bare after his secret advice to the Prime Minister was leaked.
The publication of Lord Goldsmith's report last night could prove to be the "smoking gun" that shows Tony Blair misled Parliament and the country over the war.
Last night, Mr Blair - unaware that the report was about to be leaked - was caught out still claiming on Sky News that the advice from the Attorney General "didn't change".
Professor Peter Hennessy, an expert on constitutional affairs, said: "The whole thing reeks." Dominic Grieve, the Tory legal affairs spokesman said: "There has been a gross deception."
Families of some of the British soldiers killed in Iraq said they were preparing a legal case against the Prime Minister, based on the leaked document.
The Attorney General rushed out a statement, defending his role. He made clear that he changed his view because the Prime Minister had assured him that Saddam was in breach of UN resolutions. However, it has become clear that the assurance was based on intelligence that Saddam was building up an arsenal of WMD that has proved false. Lord Goldsmith said: "What this document does, as in any legal advice, is to go through the complicated arguments that led me to this view. Far from showing I reached the conclusion that to go to war would be unlawful, it shows how I took account of all the arguments before reaching my conclusion.
"The document also makes it clear that the legal analysis might be altered by the course of events over the next week or so.
"Between 7th March and 17th March, 2003, I asked for and received confirmation of the breach of UN Security Council resolutions. It was also necessary to continue my deliberations as the military and civil service needed me to express a clear and simple view whether military action would be lawful or not.
"The answer to the question was it lawful, yes or no, was, in my judgement, yes. And I said so to Government, to the military, to Cabinet and publicly."
In his report to Mr Blair, Lord Goldsmith warned in the document that British troops involved in any invasion of Iraq might face prosecution in the international courts and said the "safest legal course" would be to secure a new Security Council resolution authorising war.
Lord Goldsmith said he believed the UK and US would need "strong factual grounds" and "hard and compelling evidence" of Iraqi breaches of United Nations resolutions before taking military action.
The six key arguments used by Lord Goldsmith to question the legality of the war were leaked at the weekend, but the full report strips away the last vestiges of defence by Mr Blair for his claim, repeated this week, that he had clear advice that the war was legal.
In the advice, Lord Goldsmith also challenged the Prime Minister's assertion that the war was justified because Saddam Hussein had flouted UN resolution 1441 on weapons of mass destruction.
Lord Goldsmith said he believed the wording of the resolution left it "unclear" whether it authorised war. "In these circumstances, I remain of the opinion that the safest legal course would be to secure the adoption of a further resolution to authorise the use of force," he said.
The advice said "a reasonable case" could be made that resolution 1441 permitted the use of military action. But it added: "However, the argument that resolution 1441 alone has revived the authorisation to use force ... will only be sustainable if there are strong factual grounds for concluding that Iraq has failed to take the final opportunity [to disarm].... We would need to be able to demonstrate hard evidence of non-compliance and non co-operation. Given the ... resolution as a whole, the views of Unmovic and the IAEA will be highly significant ... You will need to consider very carefully whether the evidence of non-co-operation and non-compliance by Iraq is sufficiently compelling to justify the conclusion that Iraq has failed to take its final opportunity." The document, leaked to Channel 4 News, states that the UK had previously gone to war in Kosovo in 1999 and taken part in air strikes against Iraq in 1998's Operation Desert Fox on the basis of advice that the legality of the action was no more than "reasonably arguable".
But he warned: "A 'reasonable case' does not mean that if the matter ever came before a court I would be confident that the court would agree with the view."