Britain and America's case for war on Iraq - that Saddam Hussein's weapons of mass destruction posed an imminent threat to the world - came close to unravelling last week.
The claims of Tony Blair, George Bush and other senior British and American figures, powerfully made in numerous speeches and several dossiers, including the February presentation to the UN Security Council by Colin Powell, the US Secretary of State, were undermined by a stream of contradictory evidence. This included the leak of a classified document in the US, the public comments of former intelligence officials, endorsed in private by their still-serving colleagues - and the testimony of Hans Blix, outgoing head of the UN weapons inspectors.
Yesterday, the credibility of the President and Prime Minister was dealt a fresh blow. The New York Times revealed serious disagreements among scientists about the purpose of two trucks which both leaders have claimed as concrete evidence of the existence of WMD, a claim repeated by Mr Blair yesterday. According to the newspaper, growing confidence that the trucks were mobile biological laboratories has faltered as they come under closer and more expert examination.
As the two supposed laboratories threaten to join a lengthening list of WMD "discoveries" which later prove to be false alarms, the public confidence of the US and UK governments is giving way to behind-the-scenes recriminations about the quality of the intelligence provided to them and whether it was manipulated for political purposes.
Mr Blix said last week that he had been disappointed with the tip-offs provided by British and US intelligence while his inspectors were still in Iraq. They had been promised the best information available, he told the BBC. "Only in three of those cases did we find anything at all, and in none of these cases were there any weapons of mass destruction, and that shook me a bit, I must say.
"I thought - my God, if this is the best intelligence they have and we find nothing, what about the rest?"
Another former UN inspector, Bernd Birkicht, said he believed the CIA had made up intelligence on WMD to provide a legal basis for the war. Supposedly top-secret, high-quality intelligence had led the inspectors on an absurd wild goose chase, he complained.
"We received information about a site, giving the exact geographical co-ordinates, and when we got there we found nothing," said Mr Birkicht. "Nothing on the ground. Nothing under the ground. Just desert." He added that a "decontamination truck" in satellite photographs presented by Mr Powell to the Security Council was a fire engine.
Cees Wiebes, a leading Dutch expert who spoke to senior intelligence officials on both sides of the Atlantic before the war, said many of them told him the WMD evidence was "very, very poor". Even worse damage was done by the publication last week of parts of a classified report in September by the Defence Intelligence Agency in the US, which said there was "no reliable evidence" to prove that Saddam Hussein had developed chemical weapons.
The same month the US Defence Secretary, Donald Rumsfeld, was saying Iraq had "amassed large, clandestine stockpiles of chemical weapons, including VX, sarin and mustard gas". The DIA insisted the report had been quoted out of context, and said it still believed there were WMD to be discovered in Iraq.
But to say that there is disquiet among the intelligence community on both sides of the Atlantic is a vast understatement. Almost every day brings fresh soundings from disgruntled officials venting their opinions. Because of the sensitive nature of their work, such officials voice their concerns anonymously, allowing ministers such as John Reid to claim they are "rogue elements". But some academics and former officials who still have close ties to the intelligence community have spoken on the record, detailing what they consider a disturbing politicisation of intelligence analysis.
Greg Thielmann is a former director of the Strategic, Proliferation and Military Issues office in the US State Department's bureau of intelligence and research. His office was privy to classified intelligence gathered by the CIA and other agencies about Iraq's chemical, biological and nuclear programmes. He said that the British and US governments would essentially be sharing the same intelligence "product" and making their own assessments of it. From what he has seen he is adamant that both skewed the analysis to suit their political needs.
To show that Saddam was a threat to the US, it would have needed to be shown that he had either developed WMD or had developed close ties with a terror group such as al-Qa'ida, said Mr Thielmann. Neither was proved.
Of Tony Blair's claims that Saddam presented an imminent threat, he believed the Prime Minister had been selective of the material provided to him by the Joint Intelligence Committee (JIC), the top intelligence clearing body. Well-placed British sources are adamant that JIC caveats about intelligence provided by MI6 and GCHQ were pushed aside by Mr Blair at the behest of his closest aide, Alastair Campbell.
One of Britain's leading experts, Dr Richard Aldrich, says as much as 70 per cent of MI6's intelligence comes from the US. Some of this comes from Israel's Mossad, which has close links with the CIA. "I think few people realise how much of our intelligence comes from the US," he added.
But was the American intelligence material "spun" before it arrived on the desks of the JIC and Tony Blair? "One of the issues at the centre of this argument is, how much of the dossier did they get from the Americans?" said Dr Magnus Ranstorp, a terrorism expert at St Andrews University. "The British have limited resources and are heavily dependent on the Americans. There was certainly a drive in the US to present a strong case of the threat of WMD."
Andrew Wilkie, a senior Australian intelligence officer who quit in protest over Australia's role in the Iraq war, believes Mr Blair should have known what lay behind the intelligence he was seeing. "I'm confident assessments in the UK of what was happening in Washington would have been made as clearly to your Prime Minister, as abundantly clear, as they were to my Prime Minister [John Howard] - that there were a far broader range of the reasons for the US doing what it was doing," he said. "I think when you superimpose that kind of assessment and that awareness by London and Canberra it makes their focus on WMD almost more mischievous."
The last word belongs with Dr Blix, who pointed out that the US and Britain "did not have patience" for prolonged UN weapons inspections before the war in Iraq. "However ... I notice now ... that when the American inspectors do not find anything, then it is suggested we should have patience."
Additional reporting by Christopher Zinn in Sydney