The explorer underwent a double heart bypass operation following a major heart attack four months ago, but today begins the Land Rover 7x7x7 Challenge, an attempt to run seven marathons on seven continents in seven days in aid of the British Heart Foundation.

It was totally unexpected, and if anyone had asked, five minutes before it happened, "How are you feeling?" I would have said very fit. But afterwards I was completely comatose for three days and nights - they attacked me with one of those electric start-up machines 13 times and I wouldn't start up, so it was relatively serious. They stitched my ribcage up with wire so, for two months, it was no driving, no exercise of a taxing nature. Even a brisk walk was out. So that left only two months in which to get from a vegetable-type state to what we're trying to do now.

I think one might have been tempted to withdraw - as soon as I started training, if I got to any kind of uphill I just had to sit down - and I probably should have withdrawn, but by that time the sponsors were involved and I was very much looking forward to it; I thought it would be an awful shame not to try. Instead, I've worked awfully hard to get fit in a carefully planned manner, radically altering my diet, and determining, with rather less success, not to allow myself to get stressed. Mind you, if I was the prime minister, I don't know how the hell I would avoid stress.

I've found that the experience has been very similar to driving along in a hurry on the motorway and seeing a crash - it makes you reassess your driving for at least half an hour, but then the bad things start creeping back in, and you start rushing again. As for my sense of mortality, when I woke up I was told that my wife had sat by my bedside for three days and nights, watching them trying to get some sort of reaction from this hunk of dead meat, which is what I was, and listening to the professor saying that if I did come to I would probably have brain damage. But all I could remember was total blackness - so if that's dying, then I'm a lot less worried about it than I was before. Meanwhile, you just have to carry on doing what you're doing. I suppose that's selfish towards my wife, but my wife knows that if she were to try to curb my activities, it would be stressful to me, and I'm trying to reduce the stress.

Nigel Jones MP

The Liberal Democrat MP for Cheltenham suffered two heart attacks last November. Two years before, he was attacked in his constituency office by a man wielding a sword who killed his aide, local councillor Andrew Pennington.

I had two heart attacks last November. I had one tiny one, where I was very ill for about an hour, and I had another one when they were giving me an angiogram. It did change the way I look at things: I follow to the letter the advice my doctors gave me - something I would advise Tony Blair to do. My doctor told me if you have a heart attack you need six months to recover. I had two, so I'm looking at a year.

In the past year I have been in the House of Commons very infrequently. I got there for the major votes on things such as Iraq, but my appearances in the Commons have been few and far between. My priorities have always been family first and work second, but when I had the attack in my office with the man with the sword a few years back, that made me change the way I did the job to make more space for the family. I could have died then - so I think that was when I really re-evaluated my priorities. But prior to the heart attacks, I would say I was still a workaholic. I was doing 80 hours a week and I've cut that down to 50. The work still seems to get done. I take my blood pressure twice a day now, and if it's risen I sit down until it has gone down. Work takes a back seat.

I've always thought that I'm pretty good at dealing with stress. I have a lot of support from my family and people in my office, but obviously part of being an MP is dealing with a certain amount of stress. So, now, if I find myself getting in a stressful state or a little bit more agitated than normal, I think: "Should I be doing this? Or should I sit down for a bit?"

Diana Moran
BBC's Green Goddess fitness presenter

I was diagnosed with breast cancer in May 1988 and everything changed immediately. Unlike Tony Blair, I decided to keep my illness a secret. I made an important decision for myself that I was going to fight this on my own. I wasn't going to tell anyone, especially the media, because they would have written me off. That is a very big fear.

The biggest change for me is that I was somebody who could never say no. I was a workaholic and in my private life I would do anything for anyone. But now I can say to myself maybe it would be better if someone else did that, it doesn't always have to be me. I have learned to differentiate the trivia from what's important.

Of course your priorities change. You suddenly realise when you are ill that your time doesn't go on for ever. You realise that if you want to do something you really have to do it now. It's a trivial thing, but I had always been interested in art but my father wouldn't let me pursue it, so I've taken up painting in oils now.

Work, if anything, has become more important. Part of it is about keeping a roof over the head, but being fit was obviously an asset in fighting my illness. Tony Blair is obviously fit too: he has an illness but the rest of him is very fit and that is so important. It is one of the reasons why I have continued to work so hard: fitness keeps things at bay.

Although I still work a lot, I have learned not to be so tense. I don't always have to try be the best.

The other thing, of course, is that you tell your children you love them. You don't normally have time or the opportunity to do that. But when you are ill you don't take anything for granted.

The illness has given me new opportunities: I'm a patron of the Breast Cancer Campaign and I do a lot of work helping people through the illness. My grandmother used to say, "Live for today with a cautious eye to the future." I've learned how important that is.

Stephen Frears
Director of Dirty Pretty Things and High Fidelity

I had a very mild attack a few years ago, and have made four films since then. I said to my cardiologist: "I thought I was supposed to be taking it easy?" And he said: "No, good God, you're supposed to be working exactly like you were before." I remember lying in hospital thinking how much worse it was for people with cancer: heart medicine these days really is terrific. Mind you, I think it would be good for the country if Blair did a little less work. It would make him a better prime minister if he delegated more.

Barry Fry
Manager, Peterborough United

The first heart attack I had, about 14 years ago, I went into hospital on a Saturday night after the game - we had another game on Tuesday and I was supposed to stay in, but I didn't: I came out and watched the game. The doctors and nurses weren't very pleased. But then I started taking a bit of notice of them, and I've been on medication ever since. When I first came to Peterborough, eight years ago, I got in trouble again, with another heart attack, and now I take four tablets a day to take my cholesterol down and the triglycerides down.

In the hospital ward [the first time], people were dying left, right and centre, and I didn't really feel as if I should have been in there, to be honest. It shook me up for a few days, but then I thought, well, if you sit at home with your feet up you might go, and if you cross the road you might get knocked down by a bus, so why not go doing something you love? You think it can't happen to you, and then it initially shocks you, but that soon goes - I've carried on because I'm doing something I love doing. There's aggravation and stress in it, but then there's aggravation and stress in being a dad or a mum or anything. That's not to say I didn't take any notice - I did, I took the medications and had a checkup every month, then every two months, and now I'm down to a checkup a year.

I've got six kids, four living at home; they and my wife have always been very supportive, though they do watch what I eat, and if the kids ever found cigars in my pockets they'd rip them up and put them in the bin. The doctors used to ask me what I drank, and I'd say lager, whisky, G&T, anything really - but they've put me on red wine for the past eight years. Not much chance of dying of a heart attack, but maybe of alcohol poisoning.

I've been in management 30 years now, and the demands are certainly greater - but no doctor's ever said, "You've got to pack up this stressful job." But running the country - I know how hard it is just trying to run a football club, being constantly in demand, abuse right left and centre and you've got to take it and your family's got to take it. So I can understand the prime minister getting in a bit of state, but I'm sure he gets a lot of satisfaction from what he does. I do. I'm 58, fat, and happy - and there ain't many of us left.