They felt it was their duty. Six of Britain's leading experts on Iraq trooped into No 10 Downing Street on a Tuesday afternoon in November 2002, determined to warn Tony Blair that occupying the country would be difficult at best and catastrophic at worst. By the time they left, most were convinced that war was inevitable - and, in the view of one at least, that there was nothing the Prime Minister could do about it.
Nearly two years later, the Prime Minister is caught in a similar bind. He would like to stop talking about the Iraq war, to focus public attention on domestic policy. But he and his advisers have had to admit to one another that the issue just will not go away.
It dogged Mr Blair last week, at home and overseas. And this week it will be in the headlines again. Apart from the growing likelihood that British troops will be deployed in Baghdad, Lord Butler, the former mandarin who conducted the official inquiry into intelligence failures in the run-up to the war, will give evidence before a Commons committee on Thursday.
One of Mr Blair's more uncomfortable moments last week was when he was reminded by the Labour MP Bob Wareing of his own words, uttered before the war. When the Iraq experts went to Downing Street on 19 November 2002, the Prime Minister and George Bush were insisting that Saddam Hussein could remain in power if he complied fully with Security Council resolution 1441, passed early that month and accepted by Baghdad just a few days before the meeting at No 10.
UN weapons inspectors were preparing to return to Iraq after a gap of four years, but they would do so against the background of a government intelligence dossier, published a few weeks earlier, which painted a blood-curdling picture of a dictator ready not only to use his weapons of mass destruction, but to share them with terrorists.
In the Middle East, the US was fast building up its forces. Britain, despite the threat of a firefighters' strike which might require troops to operate "Green Goddess" fire engines, was making its own deployments. And British and American aircraft supposedly patrolling the "no-fly" zones over northern and southern Iraq were in fact staging daily bombing raids, aimed at the systematic destruction of the regime's air defences.
The experts were not there to talk Tony Blair out of invading Iraq. "It was made clear to me beforehand that we could not talk about the advisability of war, only about what the aftermath might be," said Professor George Joffe, of King's College London and Cambridge University's Centre of International Studies. The Downing Street meeting "was not a lobbying exercise against an invasion", said Sir Lawrence Freedman, professor of war studies at King's College, at whose initiative it was held.
Dr Toby Dodge of London University's Queen Mary College, had just returned from a visit to Baghdad. "Our basic message was that if you choose to invade, it will be much, much more difficult than you may have been led to believe," he said. "I thought an invasion was a really bad idea."
According to Dr Dodge, most of the group - whose other three members were Professor Michael Clarke, director of the International Policy Institute at King's College, Dr Charles Tripp of London University's School of Oriental and African Studies, and Steven Simon, then deputy director of the London-based International Institute for Strategic Studies (IISS) - shared his pessimism.
The six men represented a formidable body of knowledge about Iraq's politics, history and economy. To hear what they had to say, the Prime Minister was joined by Jack Straw, the Foreign Secretary, Sir David Manning, then Mr Blair's foreign policy adviser and now British ambassador in Washington, Jonathan Powell, No 10's chief of staff, Edward Chaplin, then director of the Foreign Office's Middle East and North Africa department, appointed as Britain's ambassador to Iraq in June, and Mr Blair's then private secretary, Matthew Rycroft.
Over the next hour and a half the experts sought to take Mr Blair and his senior colleagues through a number of possible post-invasion scenarios, ranging from simply replacing Saddam with another dictator, though one sympathetic to the West, to a messy slide into civil war and fragmentation of the country along ethnic, religious and tribal lines.
"Much of the rhetoric from Washington appeared to depict Saddam's regime as something separate from Iraqi society," said Dr Dodge. "All you had to do was remove him and the 60 bad men around him. What we wanted to get across was that over 35 years the regime had embedded itself into Iraqi society, broken it down and totally transformed it. We would be going into a vacuum, where there were no allies to be found, except possibly for the Kurds. We were saying: 'Be prepared to spend a great deal of time and money. This could take a generation.'"
Although the outside participants were reluctant to quote the words of the Government side - Downing Street said: "It's not our policy to comment on private meetings" - what struck several of the experts was the lack of response. "There was no real argument," said one. "You sensed they were heading into a war they couldn't avoid. Although we were sitting at the cabinet table, the decisions were being taken on the other side of the Atlantic."
According to Dr Dodge, who was first to speak at the meeting, the Prime Minister said little, leaving most of the questions to Mr Straw. There was "a lot of glum silence and note-taking on the other side of the table". Professor Clarke's recollection was that Mr Blair and his officials were attentive, and "did not dissent" from the experts' opinions.
But others felt the Prime Minister was not really listening. "He was dismissive of our arguments," said one, speaking on condition of anonymity. "It seemed as if he was just going through the motions. I think he'd made up his mind already."
Another said: "I was staggered at Blair's apparent naivety, at his inability to engage with the complexities. For him, it seemed to be highly personal: an evil Saddam versus Blair-Bush. He didn't seem to have a perception of Iraq as a complex country." He recalled that the Prime Minister had interjected only occasionally and cryptically. At one point he had exclaimed: "But he [Saddam] is evil, isn't he?" Later Mr Blair said of Saddam: "But he's got choices [over being good or evil], hasn't he?"
When it was asserted that little could be achieved in Iraq without a resolution of the Palestine crisis, because that was the major source of Arab and Islamic anger towards the West, Mr Blair responded: "Yes, we must do something for the Palestinians."
The Prime Minister is credited with getting this point across to George Bush, who set out the "roadmap" for Middle East peace a few months later. The President has since been accused of neglecting the process, however, and Mr Blair has told friends he has won from Mr Bush a "firm promise" to restart negotiations if re-elected next month.
The academics differ as to the Government's intentions in November 2002. "It seemed to me that the Government was still hoping that a way out might be found, either via the UN or through a coup in Baghdad," said Sir Lawrence. Professor Joffe recalled, however: "Three of us discussed the meeting afterwards and the first thing anyone said was, 'We're going to war'."
In the chaos that has followed the war, it has emerged that the academic experts were simply reinforcing warnings Mr Blair had been receiving from his own aides for months. Leaks show that as early as March 2002, a letter from the Foreign Secretary, marked "secret and personal", said no one had a clear idea of the likely aftermath of an invasion. "There seems to be a larger hole in this than anything," said Mr Straw, noting that assuring stability in Iraq would require large numbers of troops for "many years".
A secret options paper bluntly warned: "The only certain means to remove Saddam and his élite is to invade and impose a new government, but this would involve nation-building over many years." The paper said, however, that Iraq might "revert to type", with successive military coups until "an autocratic Sunni dictator emerged who ... with time ... could acquire weapons of mass destruction".
After returning from talks in Washington in March 2002, Sir David Manning said President Bush "still has to find answers to the big questions", including: "What happens on the morning after?" He went on: "I think there is a real risk that the [US] administration underestimates the difficulties. They may agree that failure isn't an option, but this does not mean that they will necessarily avoid it." Nearly 18 months after President Bush declared major combat operations over, Iraq can scarcely be said to be under control, and even some of Mr Blair's strongest allies are admitting mistakes. The latest is Sir Jeremy Greenstock, Britain's ambassador to the UN before the war and special envoy in Baghdad after it, who now says the UN inspectors should have been allowed to complete their work.
"What has happened in Iraq was predictable and was predicted, and the worst may yet be to come," said Professor Joffe. "Iraq was a strategic blunder," said Professor Clarke. "The entire policy has become incoherent." Dr Dodge said: "I remain very much against the war. I feel I've had no influence whatsoever on the Government in the last two years." Downing Street later made a further comment, saying: "No decision about military action was taken until March 2003. Iraq has been a foreign policy priority for a number of years and you would expect the Government to be discussing different contingencies on such an important foreign policy issue."
This weekend the Blair entourage thought it had done well in the past few days towards closing down its Iraq problem. On Monday, the Prime Minister faced a meeting of Labour MPs and peers at which three backbench MPs tackled him about Iraq, but when the meeting was over the Prime Minister's own opinion was that it had gone better than the next day's newspapers suggested.
People in the corridor outside the closed meeting could hear the cheering of the Prime Minister's supporters. But some of those on the inside have complained that the atmosphere was less pleasant than it appeared. Much of the applause that accompanied the Prime Minister's speech was provided by two dozen recently created Labour peers.
When Alice Mahon, a longstanding opponent of the war, called for a Commons debate on the Iraq Survey Group findings, she was barracked by the Prime Minister's own supporters. At one point, she snapped at one of her tormentors, Phyllis Starkey, that she had a right to talk about Iraq because a member of her family was serving out there.
Prime Minister's Questions on Wednesday was also expected to be difficult for Mr Blair. As expected, it opened with the Tory leader, Michael Howard, calling on him to apologise, but he easily warded off this foreseeable attack, by throwing back in the Tory leader's face the fact that he himself supported the war.
The next day, the Prime Minister flew to Budapest for an international conference of political leaders who share his ideas on seeking out the "third way" between raw capitalism and excessive state interference. The point of this gathering was that it demonstrated that leaders who had been on opposite sides of the argument over Iraq could meet and discuss economics and domestic policy, and find their differences were not so important as what they had in common.
One of Mr Blair's fellow guests was Chile's President Ricardo Lagos, whose government held one of those vital votes on the Security Council. It was the unwillingness of countries like Chile to endorse the war that compelled the US and Britain to go in without a second UN resolution.
But when other participants held a final press conference on Friday morning, Mr Blair had already left. The Chilean President attributed his absence to "events in Iraq". Even in the pleasant setting of a Hungarian lakeside, Mr Blair could not altogether escape the long shadow of the Iraq war.