The skies over New York on the morning of 11 September 2001 were famously clear: the skies over much of the eastern seaboard three mornings later were covered by cloud low enough to have obscured the top floors of the World Trade Center, had its two towers not been destroyed. There was a hope that overnight rain would put out the fires burning in the ruins and the wreckage at Ground Zero. But the fires burned for weeks, and anyone who knew their smoke will remember it for ever.

More easily forgotten is how the fall of the towers brought down many other buildings. A few days later I helped a visiting Anglia TV film crew extricate their belongings from the 36th-floor apartment they had rented a few blocks to the south — they had been making a documentary about an animal rescue team in Manhattan. A couple of them were lucky to avoid falling steelwork; firefighters immediately behind them were never seen again.

There was no power, the elevators didn’t work, it was a long walk up an unlit stairwell with torches, each step covered in ash. The living-room of the apartment had been left in a hurry; plates of bread, a bowl of unfinished cereal, a knife with some jam on it, tea that hadn't been touched. I looked out the window. The ground was covered in girders and from that height it looked as if someone had spilt a large box of matches. There were crushed red objects among the girders; they had been fire engines. Everything about 11 September defied scale: no large TV, no cinema screenconveys how vast the scene of the destruction was. The smoke clouds that rose up when the two towers fell look big in footage of the destruction, but seen from the roof of a six-floor walk-up a mile away, they were much, much bigger.

In Washington DC that Friday there was an ecumenical service at the National Cathedral, which I watched in my apartment on Fifth and First. At the end they sang 'The Battle Hymn of the Republic', amarching song if ever there was one.

George W. Bush travelled to New York on Friday afternoon. No marching for him: his motorcade went down the West Side Highway, zipping through the fire engines that had arrived from as far away as Alabama. Phalanxes of steel workers were mustering on the dual carriageway: the scene on Christopher Street was loud as a lot of gay men cheered on a lot of straight men, including Bush. That was how things were: the spirit of a carnival one moment and on one block; at a bar on another the atmosphere drained and silent, shaken only by snatches of news that may or may not have been important— there will soon be no more burgers, we’re out of Scotch, where is Jim?

To become intoxicated by events doesn’t mean you have to have an opinion of what you encounter. I wanted to see as much as I could: I’ve never walked as much as I did that week. There was no other way of getting round much of Manhattan. You couldn’t get to Brooklyn, the bridges were closed, and it was days before phone lines to the rest of the city were restored. I walked to the New York Times building on West 41st Street to get a newspaper — it wasn’t easy to find them, and I still have the ones I bought that week. On Saturday 15 September, Anthony Lewis wrote a piece entitled ‘Beware Unintended Results’:

The American government has sounded two main themes in its response the terrorist onslaught; the United States is going to war against terrorism and we expect all other countries to support us in the struggle. The second effort, enlisting the rest of the world, is being done with particular determination and dispatch … The danger in the current situation is that hasty, ill-targeted military action could arouse anti-Western sentiments across the Middle East … President Bush, inexperienced as he is in war and statecraft, may be tempted to act quickly.

Speed proved to be exactly Bush’s temptation. He addressed a joint session of Congress on 21 September, and Tony Blair flew in to the capital to hear him speak and to begin to forge his special relationship with the American president. ‘I will not yield, I will not rest,’ Bush said at the end of his speech.

I will not relent in waging this struggle for freedom and security for the American people. The course of this conflict is not known, yet its outcome is certain. Freedom and fear, justice and cruelty, have always been at war, and we know that God is not neutral between them. Fellow citizens, we'll meet violence with patient justice, assured of the rightness of our cause and confident of the victories to come.

Less than 20 months later, on 1 May 2003, Bush gave a speech on an aircraft carrier to pronounce 'mission accomplished' of the invasion of Iraq. The speed with which the White House acted now seems impossible. It took years for the US to become fully involved in Vietnam, years to remove itself from the conflict, and years to get over it, though in the 1990s there were signs that some hadn’t: the History Channel ran endless programmes about the hardware that been used in Vietnam, and gave every indication that the US had won.

On 17 July 2003, Blair was once more in Washington. He’d been given the Congressional Medal of Freedom for being a good friend, and he gave a speech to a joint session of Congress. In it he made a joke, which now drips with irony thick as tar:

Actually, you know, my middle son was studying 18th-century history and the American War of Independence, and he said to me the other day, ‘You know, Lord North, Dad, he was the British prime minister who lost us America. So just think, however many mistakes you'll make, you'll never make one that bad.’

On the same day that Blair got his medal and spoke on Capitol Hill, David Kelly, the British weapons inspector, killed himself in a wood near his house in Oxfordshire. In the introduction to his report, John Chilcot says he had no powers to re-examine the circumstances of Kelly’s death. Nor did he investigate the motivation that drove Tony Blair to be swept up in Bush's march to war. Whatwas it about Blair’s wish for American approval, since he seems to have yearned for it? Where did this personal infatuation come from? It went over and beyond national interest. Why lose your headout of a wish not to lose the US? On the Today programme this morning, Blair was still pleading, saying he was less wrong than Chilcot said, that history would prove him right.

Blair’s offices are on Grosvenor Square, and a former diplomat I met who has been to see him there says it resembles his office on Downing St. He has a powerful neighbour, the ambassador of the United States.