Based on the commission's findings, on December 17 in Washington, Mr Bush signed into law the Intelligence Reform and Terrorism Prevention Act, the largest overhaul of US intelligence gathering in 50 years, hoping to improve the spy network that failed to prevent the September 11 attacks.

The National Commission on Terrorist Attacks upon the US (better known as the 9/11 commission) consisted of five Republicans and five Democrats, each chosen by their parties. But the crucial post of commission chairman was to be filled by the president's choice. Mr Bush's first pick was Henry Kissinger, national security adviser and secretary of state in the disgraced Richard Nixon administration. Such a choice was questionable at best, for Mr Kissinger has not only been a highly controversial figure for decades, he has long had a personal penchant for secrecy.

But before Democratic cries of 'cover-up' could rise to a roar, Mr Kissinger stepped down from the chairmanship when informed that his international lobbying firm, Kissinger Associates, would have to disclose its clients, something he had always refused to do.

Mr Bush's second choice, however, was first class. The media quickly embraced Thomas Kean, the highly regarded former two-term Republican governor of New Jersey. Not only had Mr Kean been re-elected to his second term by the largest margin in state history, he had as many friends who were Democrats as were Republican.

Born to a wealthy patrician political family, Mr Kean's grandfather, like Mr Bush's, was an investment banker. But unlike the president, Mr Kean has spent his entire adult life in public service. Widely travelled, he has visited China six times, including a 1991 journey to the panda preserve in Sichuan as a World Wildlife Fund member, and to Beijing as one of the American delegates to the UN's 4th World Conference on Women in 1995.

While president at Drew University, a small progressive college in suburban New Jersey, Mr Kean added new courses in Asian, African, Russian and Islamic studies and increased the opportunities for students to study abroad.

Why, then, would someone who has had distinguished careers in both government and academia, take on so controversial a post as chairman of the 9/11 commission? A fit man who is two metres tall and looks a decade younger than his 69 years, Mr Kean says: 'It's hard to say no when the president of the US asks you to do something - although I've said no before.'

But Mr Kean had a personal reason. 'I knew a lot of people who died on September 11, and lost some good friends,' he says. 'This is an area where many people commute to work in New York - the train only takes 40 minutes to reach the station directly under the Twin Towers. Almost a third of those killed, some 700, were from New Jersey. In the communities around here there were funerals for months.'

If the president thought that a fellow Republican might tread lightly when investigating a Republican administration, he didn't know Mr Kean well.

Asked if the continued resistance from Mr Bush surprised him, Mr Kean says: 'There were all sorts of problems with the White House. I understood them, I just couldn't agree with them. We wanted to interview [National Security Adviser] Condoleezza Rice. She was not a cabinet member, she was a presidential adviser. Traditionally, and Henry Kissinger told me this, presidential advisers never testify before Congress. And if you try to subpoena them, presidential privilege has always won those arguments.

'So to me subpoenas were always a last resort. Firstly, I didn't want to fight subpoenas in court - I didn't have time. Every president since Franklin Roosevelt has been upheld in courts by presidential privilege. The only time when the courts sided against a president was in a criminal investigation, as with the Nixon administration. So our chances of winning a presidential privilege argument in court were not large.

'Secondly, people under subpoena act differently. They come in with their lawyers and are very guarded in their answers. The president didn't want this either, but everyone knew it was out there. We did issue about three subpoenas, including one to the Federal Aviation Authority, when they were not giving us material we wanted.

'I understood the presidential argument. What they were worried about, aside from allowing Ms Rice to testify, was about certain presidential papers that we had to see - the Presidential Daily Briefings [PDBs] are the most highly sensitive documents that the government processes. No Congressman had ever seen them. Even my vice-chairman, Lee Hamilton, who chairs the Senate Intelligence Committee, had never seen them. And the reason they don't see them is that presidents have said, if advisers writing these memos know that some day their notes might be made public, they'll write them differently. That's absolutely right, and I understand that.

'Their argument was that: 'If we give these documents to you, then a Congressional Committee will come in right behind you and we'll have a much more difficult time. And this will not only damage this president, but future presidents.'

'But from our point of view, we couldn't tell the public what the president knew and when he knew it, unless we heard from Condoleezza Rice, who was right in the middle of 9/11. We couldn't do our job. My argument was: This is a unique event. This is a unique request. We're not setting any precedent.'

Rather than use legal threats, Mr Kean applied public pressure by keeping the media informed of the committee's progress and the road blocks slowing that progress. He fought for and got his budget increased, allowing him a staff of 80 people. He also fought for more time to fully complete the committee's work, and got that as well.

'They [the White House] were a little upset that we were so visible in the media,' Mr Kean said. 'But I felt that we needed to be visible and transparent, not only for the public and the press, but also for the families.'

As pressure mounted on the White House, the man who Mr Bush lauded as being 'a leader respected for integrity, fairness and good judgment' was now being labelled 'unreasonable and stubborn'.

Mr Kean was resolute in having his committee's 10 commissioners gain access to the PDBs, to the president's staff - and to the president. 'The rumours about the PDBs were already out there, particularly by people who had deep suspicions about the president,' he said. 'But the rumours were much greater than what the documents actually showed. We had all sorts of inquiries from people who were absolutely sure that the PDBs had talked about bombs on planes, had talked about planes being used as bombs. And one of the things that we had to put to bed were the so-called conspiracy theories, which weren't correct.'

When Mr Bush finally submitted to being questioned by the commission, albeit with vice-president Dick Cheney by his side, and not under oath, Mr Kean gave him high marks.

'When Bush finally spoke to us he was terrific,' Mr Kean says. '[Bill] Clinton had been terrific as well, but I think people expected him to be. With Bush, we didn't know what to expect. He has a reputation of being inarticulate, and we didn't know what he was going to be like. Press conferences aren't his best forum. But this was in the Oval Office with only about 12 people, and I've never seen him so good.

'We were told originally that that session was to be set for two hours. But when we weren't finished in two hours, the president said: 'I'm not going to leave here until I've answered every one of your questions.' On several occasions I had to interrupt other commissioners to ask them to move on to other questions. But Bush said: 'No, I'll answer.' He stayed for three hours, and still said 'Are there any more questions you want to ask me?' Later, one of the Democrats said to me: 'If that [session] had been public, he'd be up 10 points in the polls.''

Mr Kean says that, contrary to countless political cartoons, Mr Bush dominated his session, with Mr Cheney only speaking when spoken to.

The 9/11 commission's report has been highly praised by American political leaders and the media for the depth and breath of what it revealed. One main criticism is that nowhere in the report is any single government official blamed for the greatest intelligence failure in US history.

The report does hammer the CIA, the FBI, the National Security Agency and the Federal Aviation Agency for a host of failures. And Mr Kean has stated repeatedly that September 11 could have and should have been prevented. But by spreading the blame so broadly there seems to be no one to blame.

Questioned on this stance, Mr Kean says: 'It was the system that failed. We gave examples where good people overcame a bad system, including a Florida immigrations officer who deported one of the would-be hijackers because he was suspicious.

'We didn't see how listing those 10 other immigration officers who were standing at the gate when the other terrorists came in would help our cause or anybody else's.'

Mr Kean also cites the case of Zacarias Moussaoui, the Arab militant who wanted to fly jets.

'The FBI caught Moussaoui, arrested him for an immigration failure, identified him as an Arab militant who was trying to learn to fly jumbo jets. This information was shared with the CIA, and it went right up to [CIA Director] George Tenet. So Tenet knew about it. The FBI also reported it to their people in Washington. But it got stuck in the bureaucracy, and never reached the FBI director. We asked Tenet: 'Shouldn't this have been in the president's briefing - an Arab terrorist learning to fly jumbo jets?'

'Tenet's answer was: 'That was an FBI case.' That's the culture of these agencies. That's where the failure lay. And that's what needs to be fixed.'