Whatever else the Chilcot inquiry does – and I still believe it won't be much – it will at least have served to remind people just what a disastrous exercise the whole invasion of Iraq was and how Tony Blair must carry the personal responsibility for it. In overall terms the evidence so far has changed little of the picture we already knew. But in testimony after testimony of the players involved it has filled out the picture of war that was fought on the flimsiest of excuses, conducted with the minimum of preparation and pursued in blithe disregard for its consequences.

Which is why, of course, Tony Blair is apparently so furious that Chilcot has rained on his parade just as he was hoping to become President of Europe. And it is why presumably he has chosen to come out and say in a BBC interview last Sunday what we had all suspected but never quite believed would come out in the open – that he was determined on regime change in Baghdad come what may and that, if he hadn't had weapons of mass destruction as a reason, he would have found another.

Again it's not new exactly. Tony Blair said right from the start that he believed the removal of Saddam Hussein an end devoutly to be wished, whether or not WMD were discovered. He said that much in a speech in Glasgow in February 2003 at the height of the demonstrations against it. But that is not exactly how he sold it to the Commons or the people, when WMD were used as not just the proximate reason for war but its urgent necessity.

How did he get away with it? Much has been made of the "revelations" of the procession of officials and generals who have appeared before the Chilcot Committee to explain that they were concerned that the evidence that Saddam Hussein possessed WMD was so thin, that they were worried that there was so little planning for the post-invasion period and that they were taken back at the extent to which the Prime Minister was going along with Washington's plans without exacting anything in return.

Indeed they may have been. But if they were that concerned there is precious little evidence that they did anything about it. Senior officials from the Foreign Office turned up before Chilcot to whine about how they were kept out of the loop of Blair's planning, with the implication that somehow it might all have been different if they had been brought in. Sir Jeremy Greenstock, our representative to the UN before the invasion and in Baghdad after, even declared that he was prepared to resign if another UN resolution went against us.

Prepared to resign? Anyone who has ever worked in an organisation knows that the threat of future resignation isn't worth the paper it isn't written on. As for the suggestion that all these figures were against the invasion at the time, all one can ask is: "What did you do about it then?" (Not that Chilcot's committee ventured to ask.)

Major General Tim Cross, who liaised with the US on reconstruction, declared that he urged the Prime Minister in a private conversation two days before the invasion to delay it until post-war plans were better prepared. Two days before, with the troops already assembled and on the move, and a senior officer honestly thought some mildly expressed concerns would stop the ball from rolling? What kind of soldiers are we promoting to generalship these days.

The answer is the same kind of men (for they are all men) that we've witnessed throughout these hearings, masters of bureaucratic temporising with an eagerness to please their political masters matched by an equal desire to evade responsibility if things go wrong.

In all the evidence before Chilcot not once did we get a diplomat who said that the Foreign Office had so downgraded its Middle Eastern expertise that it no longer understood Iraq let alone could advise on what to do there. There was not one admission by the intelligence services that their competence in Iraq was virtually nil, although they claimed more to please their political masters. Instead we got a litany of excuses and pretences in which nothing was anybody's direct responsibility, it was all the fault of No.10 or the Pentagon or the White House, everybody was at fault except the officials before Chilcot.

The invasion of Iraq was one of the most damaging acts of post-war British politics. The decision to go in, the total lack of preparation for the aftermath and the insouciance to its consequences, was down to one man and his relationship with a US President bent on reshaping the world in America's own image. But that Blair was able to proceed for the weakest of reasons is also down to a Commons that allowed him to roll over them and a bureaucracy too supine and self-regarding to stand up for what they say now they believed in then.

a.hamilton@independent.co.uk