Having read that General Colin Powell insists on punctuality, I arrive an hour before my appointment at his office - which is in a leafy part of Washington DC - planning to find a quiet corner to go through my notes as I wait. There is no one else around but, as I'm entering the building, a silver sports car roars up: a brand new, six-litre V8 Corvette. I'm pretty sure it's him behind the wheel, and equally sure he hasn't clocked me.
''I saw you arriving,'' he says when we meet an hour later. Of course he did.
Like Tony Blair and George Bush, he must have to watch out for strangers on his doorstep, or rather loonies and conspiracy theorists wishing to protest about the Iraq War. Although Powell advised Bush to delay the invasion and give the UN inspectors time to do their work, he ultimately failed to rein in the hawkish Dick Cheney and Donald Rumsfeld and then, with his 2003 speech to the UN that accused Saddam Hussein's regime of ''concealing their efforts to produce more weapons of mass destruction'', he gave a veneer of respectability to the war. Or so his critics claim.
In the corner of his office there is a 19th-century saddle, one used by the Buffalo Soldiers, the nickname given to the Negro Cavalry. On the walls are photographs of Powell with the four presidents he has served, going back to Ronald Reagan. I study them as our photographer takes his last shots, then I look down and see the Corvette parked in the courtyard below. Nice car, I say. But I'm surprised he doesn't have a driver and bodyguards. ''No, I dispensed with my security team exactly six minutes after Condi took over from me at the State Department,'' he says.
That was in 2005, when Condoleezza Rice became Secretary of State, only the second black person in history to hold that office - Powell being the first. ''There were about 20 of them,'' he says. ''And they used to guard the whole street. My neighbours loved it. Safest place in northern Virginia. But I wanted to be able to drive myself so I said, 'Guys, you've been wonderful. You're all relieved of your duties.' '' What about public places? ''When I'm flying I go to the airport in a baseball cap and windbreaker and I stand in line and talk to people. I also like to sit and watch people go by, and I've come to the conclusion that most Americans need to be on a diet, and need a dress code.''
At 75, Powell is still a physically imposing 1.88 metres tall with broad shoulders.
And he does still get recognised, most of the time.
''I was coming back from Jamaica and a German couple were getting off the elevator and the husband said to his wife, 'Look, Frieda, look, you know who that is? It's General Schwarzkopf.' '' His new book is full of such self-deprecation. Called It Worked for Me: In Life and Leadership, it is an odd mix of the profound and the quirky, such as his hobby of fixing broken down old Volvos. ''Well, I am quirky!'' he says when I point this out. ''In my first memoir I had to cover my experiences as the chair of the Joint Chiefs of Staff and national security adviser and when we were halfway through, my collaborator looked at me and said, 'Do you know how boring this ---- is?' So this book has more of the quirky stuff.''
As well he knows, that earlier memoir, which was published in 1996, was far from boring, which was why it became an international bestseller. Not only did it cover his time as a war hero in Vietnam and the small matter of his being in charge of the First Gulf War (he was General Norman Schwarzkopf's boss), it also showed how he was the embodiment of the American dream, rising from a modest childhood in the Bronx to a glittering career, first in the army then in politics.
This new book doesn't so much take up the story since then as use anecdotes about his career to explain his theories about leadership - one such being that any organisation should make sure its employees aren't afraid to deliver bad news. A good example is the way no one dared show Rumsfeld (then Secretary of Defence) the Abu Ghraib prison torture pictures, which meant the problem was allowed to grow. I ask if another example might be the way that, in the days before his ''infamous'' (his term) speech to the UN in 2003, US intelligence chiefs didn't share their doubts with him regarding their own claims about Saddam's WMD capabilities.
This is an uncomfortable subject for Powell.
He has referred to it as a ''blot'' on his record. His wife, Alma, has gone further and said that he was ''callously used'' by the White House. He was enormously popular, you see, and polls showed him to be the most trusted man in US politics.
The intelligence community knew the information he was going to reveal was suspect, but no one dare admit it to him; was that it? ''Not just me, they weren't telling their intelligence superiors,'' he says. ''Some agents have since claimed that they tried to tell their superiors, but the superiors say they never did. All of us, me, the president, our British friends, all accepted what we were being told, without knowing there were serious weaknesses.''
It takes courage to admit to your boss that you don't know something. ''Yes, it takes courage from a junior coming in who is about to get his head taken off if I don't like what he says. But you also have to create an environment where, if your people know more about something than you do, then they will tell you. 'Tell me what you know and don't be put off if I argue back with you. I am arguing with you to get everything out of you I can, and then I'll make a decision'.''
Powell writes in the book about how a General has to trust his instincts in war. Did his instinct fail him on that occasion in 2003, to the extent that he failed to ask the right questions?
I'm thinking especially about the single source, the agent known as Curveball, who claimed that Saddam had mobile laboratories to conceal biological weapons.
''I didn't know of a Curveball at the time of my speech, I didn't know there was a single source,'' he says.
Were they telling him information hadn't come from a single source?
''Yes. They told me there were multiple sources. I wouldn't have accepted it if it was just one guy in a German detention camp. A lot of the things that were in the basic intelligence document that was sent to Congress four months before my speech, I challenged - not because it was wrong, but because it had a single source, or just didn't sound right. But with respect to what I did use at the UN, all the leadership of the government was behind it, including Congress. It was four months later that the president said, 'OK, take the intelligence document and make a presentation on it to the UN.' ''
He wasn't given enough time to do the job properly, but rather was bounced into it? Was that it? ''Rather than starting from a running position we had to start from a stationary position and create the presentation in four days,'' he says. ''It didn't bother me because I had seen the whole intelligence document. I thought we could do this. Frankly, a lot of the stuff will stand the test of time. Saddam was a guy who did use that kind of technology against his own people and against the Iranians and there was little doubt in anyone's mind that if he had been relieved of UN sanctions, he would be right back in the game.''
Powell knew that better than most because of his involvement in the first Gulf war, when Saddam definitely did have chemical weapons.
''Yeah, he had stocks of it,'' he says. ''To this day it is a mystery what happened to them.''
Does part of him still think maybe it is buried in the Iraqi desert somewhere? ''There are conspiratorialists who still think that, or some who point to Syria, but that's an excuse. I don't see anything, and haven't seen anything in the last nine years, that would suggest it was moved to Syria or it was buried in the sand, even though, after the first Gulf war, we found jets buried in the sand. Fact is, there weren't any programs. And remember the argument we were making was not one of potential use, but that they had it.''
Did Powell support the president?
''The truth is, I thought we should see if there was a way to get rid of this problem of WMDs through diplomatic and peaceful means. I spent time with the president on that proposition and he accepted it. He went to the UN and asked for a resolution to do that. But Saddam failed the first test of it by giving us worthless documents when we said 'show us what you got'. When he didn't show us, and the president and Mr Blair decided we should take military action, I fully supported it and you will find nothing in the record from the UN speech and onwards that I spoke against it.''
And before then, did he advise … He stops me. ''Look, if this is going to be all about this, we might as well stop.'' Surely he can understand my curiosity. It was an extraordinary time. ''Well it is an extraordinary episode, but it is what it is.''
OK then. Change of subject. To what extent did his time in Vietnam inform his attitude to military engagement? ''Well, it was my war. I spent two years there, at the beginning when it looked so noble, and at the end when it didn't look quite so noble. I am a professional soldier who has studied war all his life, from ancient philosophers to Sun Tzu and Clausewitz, and my own thinking is that you should always have a clear political objective before you decide to use the last resort, which is force, which kills people; not only the enemy, but your own folks and the innocent civilians who get caught up in the conflict.''
That's why they call him the reluctant General?
''You bet I'm a reluctant General,'' he says. ''I've seen war. I've run wars and I think our civilian political leaders have an obligation to think things through as best they can, with as much time as they have before having to make a decision, to see what the consequences are.''
Run for president
I ask him to talk me through his thinking in 1996 when everyone was telling him to run for president - his polls were through the roof and even Bill Clinton, who went on to win, was saying that Powell was the one man he didn't want to face. Was his heart just not in it?
''There was a lot of speculation and I foolishly said, 'So many people are pressing me on this I will have to think about it.' That raised the temperature even higher, but after six weeks of not having a single morning where I got out of bed and said, 'This is what I want to do,' I realised I didn't have the passion for the job a potential president must have. It just ain't me. I decided the speculation had got out of control and we had to shut it down. My wife looked at me and said, 'What took you so long?' She had become part of the story because she suffered from depression and Time magazine was making a big thing of it.''
And no regrets? ''No, none.''
Not even on the day when Barack Obama became the first black president? Wasn't he a little wistful then? ''No, no. I have a habit of making a decision and moving on.'' He may not have been a political animal, but he was a natural-born soldier. ''Yes, I responded to the structure, discipline and camaraderie of the army. You can't imagine what it was like as a black kid going in the army in 1958, four years after the last black unit had been disbanded. We still had segregation in the South. There were still strong views in the country that black people couldn't make good soldiers. But there was another current which said we've got to move them on, we've got to give them the opportunity. I think I was penalised in one sense but given an advantage in another, and my view was that whatever advantage you are given, take it and don't feel guilty about it because there have been 200 years of black people getting nothing.''
He believes black people in the US have always had an affinity for military service because they thought it was the only way they could prove themselves the equal of a white person.
''Get armed like one and shot at like one.'' He speculates that if his parents - who before becoming naturalised Americans were British citizens - had taken a boat from Jamaica to Portsmouth, instead of New York, he would only have been able to rise to the rank of sergeant.
''The British Army still doesn't have a black General,'' he says.
We are on the subject of the special relationship now. He reckons the closeness comes from common beliefs in democracy, freedom and individuality ''and it has always been there, apart from the War of Independence''. You just won't let it go, will you? ''Well, you burned the place, man!'' He says this with a deep laugh.
He doesn't think Alma would have cared if he had never risen above the rank of lieutenant colonel. ''There is all sorts of baggage that comes with high office,'' he says. ''Working late. The kids have to stay out of trouble - fortunately mine did.''
Judging by the way he constantly refers to his wife, he is an uxorious man. He is also a good raconteur, and even his enemies don't deny his fundamental decency and charm: a good man in a bad administration being the usual line. He has an endearingly wheezy laugh and a slightly less endearing way of being pleased with his own folksy anecdotes, as rehearsed during his speaking engagements.
''They always laugh at that bit,'' he will say, or, ''That one brings the house down.''
As we have seen, he likes to think of himself as quirky, even as a boss. ''I liked to be goofy sometimes in meetings but people also knew: 'Don't screw with me because I can make you cry if I have to. I can be nasty. I can spoil your day.' But I've found I get better results if I try to be affable. As well as being firm and setting high standards and forgiving errors, I like to have fun.''
He also does a good Ronald Reagan impersonation. There was clearly a chemistry between them, I say, but I'm sensing not so much with the other presidents.
''I got on well with all of them. They all had different styles. My job as a staff person is to adjust to their style, not expect they would adjust to mine.''
He has said in the past he found Bush's fidgety impatience irritating, along with his tendency to interrupt everyone. What about W's habit of closing the door on him if he was late for a meeting? ''He did that to everyone, even Karl Rove [senior adviser]. It was more a joke than trying to diss me.''
There were days when every king, every president, every prime minister in the world was calling him, and every reporter wanted to hear what he had to say or think. ''One day you are the number one diplomat in the free world,'' he says. ''Next day you ain't.''
What was it like to go from having one of the most high-pressured jobs in the world to being an ordinary citizen? Did he feel lost? ''They pull out the phone, the bodyguards go away and you lose your private plane. You have to transform yourself and become something different. That begins at home.
''I was sitting at home with my wife and I said, 'Darling, this is the first day of the rest of our lives. I won't be leaving the house at 5.30 in the morning any more.' She froze. Then I could hear her muttering under her breath, 'This fool doesn't know how we stayed married for 50 years.' '' He tells me he sleeps better nowadays. ''Never pass up the chance to have a nap in the afternoon. Now I'm on my way to 76, I always try and nap for 20 minutes after lunch.''
We have gone over our appointed hour. He is now running a little late for a lunch with another General but, nice guy that he is, he nevertheless offers me a lift in his Corvette. Sadly, I have to decline as my hotel is literally just a couple of hundred metres away.
But I do enjoy watching him roar off, driving himself, a free spirit without bodyguards.
It Worked for Me: In Life and Leadership by Colin Powell is out now (HarperCollins, $35).
London Sunday Telegraph