Alan Watkins: The guilt for this debacle is spread wide, and Gordon Brown cannot escape blame

There is no period more remote, no age darker, than the day before yesterday. We have already forgotten exactly how Mr Tony Blair took this country into Iraq. It is the largest single misjudgement of British foreign policy since the war. That includes and supersedes the Suez operation. The last couple of weeks have seen the beginning of the retreat from Baghdad and its vicinity, which for future purposes takes in most of Mesopotamia.

The retreat has been led by the United States; just as it was the United States which took us into that now even more unhappy country. The general outlines of what happened are clear enough, as they always have been. But the precise sequence of events has already silted over.

The principal actors are, mostly, still with us: Mr George Bush, Mr Blair, assorted auxiliaries attendant on their respective leaders, civil servants of both the national and the international variety. The more minor players, or those who had a part in the crowd scenes merely, have tended to merge into the background. Among them are the members of the House of Commons; or, rather, they were the members elected in 2001; though most of them are still parked on the green benches and are continuing to fill in their expenses claims like billyo.

The political truth is that Mr Blair would not have been able to take us into Iraq at all without the authority and consent of the Commons. The rest is persiflage, a lot of exulted constitutional chatter about the royal prerogative to declare war and the powers of ministers to conduct military operations. If the House had voted against the war in Iraq, the Prime Minister would not have been able to take matters further; or not, at any rate, in the direction he had chosen.

The accepted wisdom, both at the time and subsequently, was that in that event Mr Blair would have had no choice but to resign. Alternatively, the entire government would have been compelled to take its leave. I do not think that either of those conclusions would have come about, in practice.

Clearly the entire government would not have had to resign. The country was not taken into war by the Cabinet but by the Prime Minister and a handful of Downing Street apparatchiks led by Mr Alastair Campbell and Mr Jonathan Powell. Their colleagues, uninvited to perch on the No 10 sofa - indeed, positively discouraged from taking a seat - would have breathed a sigh of collective relief and sent for Mr Gordon Brown instead.

But would Mr Blair have had to depart on his own, accompanied only by a few of his obedient aides? The assumption, then and later, was that he would have had to go, if he had lost the vote. Mr Blair not only made the case for war: he believed in the case that he was making. It is a form of insanity. It is his greatest strength as a politician.

But then there is a setback, even an outright defeat; and, all of a sudden, there is a change. It can range from our entry into the euro to the establishment of a quota in so-called faith schools. Then he forgets all about it, or turns his attention to other subjects. In one of his favoured canting phrases, he "moves on".

My guess - though it is slightly more than a guess - is that if Mr Blair had been defeated, he would have moved on from Iraq too. He would have made the best of things, but he would still have stayed on in No 10.

Let us take a stroll through the yellowing pages of Hansard (with additional information supplied by the excellent House of Commons Information Department). There were two crucial divisions, on 26 February 2003 and 18 March. There were four divisions in all, because each principal vote was preceded by an amendment, on both occasions moved by that invaluable former member Chris Smith.

The February motion, moved by the government, supported "the government's continuing efforts in the United Nations to disarm Iraq of its weapons of mass destruction" and called on Iraq "to recognise this as its final opportunity to comply with its disarmament obligations". The amendment claimed that "the case for military action against Iraq" was "as yet unproven".

The Labour vote was 255-122 against the amendment; the Conservative, 130-14 against; the Liberal Democrats voted solidly for. On the substantive motion, Labour voted 274-60 in favour; the Conservatives, 152-0; once again, the Lib Dems were solidly against the government. If all the Conservatives had voted against the government, the motion would have been defeated.

The March motion, moved by the government, was very long. It said, among other things, that the government "should use all means necessary to ensure the disarmament of Iraq's weapons of mass destruction". And offered "wholehearted support to the men and women" of the armed forces "now on duty in the Middle East". The amendment believed that "the case for war against Iraq has not yet been established".

The Labour vote was 247-139 against the amendment; the Conservative, 140-16 against; the Lib Dems were unitedly in favour. On the substantive motion, Labour voted 256-85 in favour; the Conservatives, 147-3; once again, the Lib Dems secured a full turnout against the government, apart from one member who did not vote.

The final Iraq motion was passed by a majority of 263. One-fifth of the Parliamentary Labour Party voted against the government but three-fifths in favour. Sixty-two per cent of Labour MPs voted for Mr Blair but 90 per cent of Conservatives were for him too, while there were no Lib Dem investors at all in the government side.

There were some curiosities. Thus Mr Robert Marshall-Andrews came up to expectations, voting for both amendments and against both motions. But Ms Vera Baird proved less steady on parade, voting for the government in February and not voting at all in March. And those usually rebellious spirits Mr Andrew Mackinlay and Mr Michael Meacher voted the straight, Blairite party ticket all down the line. So one could go on.

In September, Mr Blair said it had not been his party's finest hour. He was talking about something else; or perhaps it was the same thing in a slightly different form, in this case the departure of the Prime Minister and the succession of the Chancellor. Alas, Mr Brown has hardly covered himself with glory either, any more than the Labour MPs have. The party motto is not now some snappy quotation from Karl Marx or the Methodist hymn book but from Fawlty Towers: For God's sake don't mention the war.