Richard Clarke is the man who put the cat among the pigeons. This year, in the same week as the former counter-terrorism chief was giving evidence to an independent commission investigating the attacks of 11 September, Mr Clarke's scathing account of the failure to deal with al-Qa'ida was published.
In his tell-all memoir, Against all Enemies, and in his public testimony, Mr Clarke could barely have been more provocative. Much of the blame for failing to stop the attacks of 11 September, he said, could be laid at the feet of the Bush administration. They ignored his warnings about the threat posed by Osama bin Laden and - after al-Qa'ida had wreaked havoc and death in New York and Washington - President George Bush was distracted from taking on the terror network by his groundless wish to invade Iraq.
"Your government failed you," Mr Clarke told the hearing, turning to the relatives of those who died and who had come to Washington to hear his testimony. "Those entrusted with protecting you failed you. And I failed you. We tried hard, but that doesn't matter, because we failed."
Not surprisingly, the administration hit back immediately. Mr Clarke was wrong, said officials. He was out of the loop, said Vice-President Dick Cheney. The White House now considered Mr Clarke an outcast.
He is a blunt, plain-spoken man, accused by some former colleagues of arrogance and even rudeness. But does he regret speaking out. "No, not at all," he said. "I always thought, particularly in a White House job if you placed a high value on being liked by the bureaucracy, if that was one of your primary goals, then you probably should not be in that job.
"The job of a White House NSC [National Security Council] staff person is to be an enforcer of presidential policy. The bureaucracy does not naturally do what the President tells it to do."
But Mr Clarke's complaint is that the President and his senior staff, in the spring and summer of 2001, failed to listen to what he advised them about the dangers posed by al-Qa'ida "when maybe we could have done something to stop 9/11". The day after the attacks, Mr Bush was already focusing on Iraq. "Look into Iraq, Saddam," Mr Clarke says he was told angrily as his officials briefed him on al-Qa'ida being almost certainly responsible for the attacks.
Mr Clarke, who now has a consultancy firm in Arlington, Virginia, remains uncertain whether al-Qa'ida could have been stopped. "I don't think we know. It's very facile to say it could have been or could not have been. There is absolutely no way of knowing. What I do believe is that had we known about the two al-Qa'ida individuals who were among the hijackers ... Had we known they were in the country, which the FBI at some level knew and which the CIA at some level knew, had my counterparts at the FBI and CIA known, had I known, then I firmly believe we could have caught those two.
"Now, you can draw all sorts of conclusions from that. One, is that, simply, there would have been 17 hijackers. Another conclusion is that we might have been able to pull strings on those two and find more of the 19. But even if we had rounded up all 19 there would have been another 19. There would have been another major attack. The point is that al-Qa'ida was on a march to have a major terrorist attack ... They would not stop until they succeeded in having one. So yes, we might have been able to stop a particular attack."
Apart from the missed opportunities he highlights, what might be of potentially greater concern is Mr Clarke's belief that al-Qa'ida could easily attack again, and America and Britain remain exceedingly vulnerable. Another attack is not inevitable ("I think almost nothing is inevitable," he said) but possible.
He added: "I think it is harder but I can think of ways of them doing it and I'm sure they can imagine ways of doing it. It's entirely possible there will be another major attack." A dirty bomb, he believes, is probably in the "too hard" category. It is more likely terrorists would use suicide-bombs to attack softer targets, such as casinos or shopping malls. "Those are the two scenarios I use all the time when discussing it," he said. "If you do eight guys in eight shopping malls you have an enormous effect on the economy ... so much of the US economy is tied up with retail sales.
"If you did four casinos with four guys you could destroy the economy of Las Vegas. There are lots of low-end ways of doing things. And the reason they have not done some of the low-end threats, I think, is because they set the barrier for themselves very high with the 9-11 attacks. They may want another major attack; they may feel that if they do less than a major attack [they] will look like a lesser force."
Richard Clarke has made a career out of telling uncomfortable truths. He was born in Boston, his mother a nurse and his father a worker in a chocolate factory. In 1961, aged 12, he won a chance to attend the prestigious Boston Latin School, whose famous former pupils include Benjamin Franklin and Samuel Adams. From there, Mr Clarke - an active opponent of the Vietnam War - went to the University of Pennsylvania to study for a career in national security. "I wanted to get involved in national security in 1973 as a career to make sure that Vietnam did not happen again." He spent five years in the Pentagon and then moved to the State Department. In 1992, he was taken on by the White House as a national security staffer. One of the first things he did there was to exert greater influence on the Counter-terrorism Security Group. Though his career stretched over four presidencies - Ronald Reagan, George Bush Sr, Bill Clinton and George Bush Jr - it is the last for whom he reserves his most outspoken criticism. The American people were duped, he believes, by Mr Bush who came to office with a plan to invade Iraq but hid it during the election campaign. "It was very clear on 9/11, on the days immediately following when we had been attacked, that attention turned to Iraq, even as the smoke was still coming out of the World Trade Centre."
Mr Clarke believes Mr Bush's decision to invade Iraq undoubtedly damaged the hunt for al-Qa'ida. He also believes it has diverted much-needed resources from Homeland Security, leaving the country unnecessarily vulnerable. "[Iraq] is a fiasco," he said. "We can only hope there is a way of minimising the losses and getting out in a way that allows us to leave behind some sort of stable government. If [it stays as it is] now there is a high risk that what we leave behind will be worse than what was there before ... Iraq could easily be much more of a problem for us than it would have been if Saddam Hussein had stayed in power."
The whistleblower highlights three ways in which the invasion of Iraq diverted resources from the real "war on terror". Money is not available for the Department of Homeland Security to protect potential targets such as trains and chemical plants adequately, funds are not available to help countries such as Pakistan and Yemen, which could do more to counter terrorism.
Finally, the war was a great propaganda coup for the jihadist movement. "It probably greatly increased its recruitment," he said. "There was a period of time as well ... where resources in the hunt for Bin Laden were pulled away, satellite resources, special forces, Predator [drones] were sent to Iraq, rather than sent to Afghanistan. That has been somewhat rectified but not entirely. If Bin Laden had written the scenario it would have been identical to what happened."
One of Mr Clarke's friends from the national security council, is foreign policy adviser to the Democrat presidential nominee John Kerry. Mr Clarke has refused to endorse Mr Kerry in his bid for the presidency. "I do not want to be seen simply as a politically partisan commentator," he said. "I was a career civil servant. We don't have as much a tradition of career civil servants as you do [in Britain] but we have senior executive service and I was a member of that for a long time. I have a lot of Republican friends and they agree with me on most of what I say.
"So I don't want to lose the support of large numbers of Americans by my choosing sides, by choosing parties. I think this issue should be non-partisan. A large number of Republicans agree with me and I want them to speak out."
Education: Boston Latin School and University of Pennsylvania
Career: 1985-88: Deputy assistant secretary of state for intelligence
1985-92: State Department
1989-92: Assistant secretary for politico-military affairs
1998-2000: National co-ordinator for security, infrastructure protection, and counter-terrorism
1992-03: Chair of the counter-terrorism group, National Security Council
March 2004: Testified to national commission on terrorist attacks
Author of 'Against All Enemies: Inside America's War on Terror - What Really Happened'Reuse content