'The sort of travel I do is not spending two years going from Norway, arriving back at Norway and telling people about polar bears and Eskimos,' he says.

'The real travel is what happens inside you, how you as a human get to know yourself. How you make decisions; how you look at problems; how you know your limits. It's not going around the world - I can use an aeroplane for that, and what do you experience in an aeroplane?

'The real story is how I travel inside myself. The world has been mapped, but humans haven't been fully explored.'

On the trip, Horn dragged a custom-built Kevlar sled full of supplies behind him, while using a kite to speed himself along the ice plains when possible - although it usually was so cold that he had to walk to generate enough body warmth to stay alive. At stages on the imaginary 66 latitude circle where he had to cross water, a kayak and a four-metre yacht were ready waiting for him.

The idea of spending two years in the freezing temperatures and twilight of the North Pole - a place so cold that you have to defrost your face before going to sleep lest it sticks to your sleeping bag - isn't exactly a comfortable one. Horn recalls when, faced with 160km/h winds, he was unable to pitch his tent and was forced to walk solidly for 72 hours.

In Russia, he was arrested for entering a 'restricted area' and sent back to Alaska to get a permit, while the local mafia held his boat as ransom. Horn explained that he'd leave without the boat if he had to, and so managed to get it back.

'I've got my feet on the ground,' he insists. 'I've got two arms, two legs, a head, I love what I do. But passion isn't always easy. We don't always do it with a smile on our faces, so it's important to take the good moments as you'd take the bad moments. It's only after you've had a bad moment that life can get better.'

Before completing this latest mission, Horn was already the first to circumnavigate the equator, travelling un-motorised at latitude 0 in 2000.

'It's complicated,' he says. 'My father played for the Springboks, so it was second nature to do sports in my family. I always thought it would be wonderful to earn a living in this way. But because of the South African boycott, all the apartheid - I was more or less punished for it. I didn't vote for apartheid, I was only a kid at that stage. And then all of a sudden I was denied the chance to compete. My generation had to assume responsibility for that.'

He has spent the rest of his life making up for it. After gaining a degree in sports psychology at Stellenbosch University in Cape Town, Horn left South Africa 11 years ago to travel, ending up working as a ski instructor in Switzerland. That became the springboard to a career that has seen him both swim and trek the entire length of the Amazon - 7,000km, alone - and kayaked off a 22-metre waterfall in Costa Rica.

In Switzerland he met his wife, Cathy, with whom he has two daughters - which brings into focus the issue of how a record-breaking adventurer reconciles life-threatening ambition with the responsibilities of parenthood.

'You must know how to give, to take. My family gives me the freedom, but what do I give them? I take the freedom and I do what I do, but it doesn't come for free,' he says.

'Is it better to be someone who goes to work before his kids wake up, and then comes home when they're in bed? You're at home all the time, but you never see your kids anyway.

'I'm always there, but I'm never there. When I communicate over satellite or they came to visit me once every six months on a stop, it's emotion that binds the family. We all know what I'm getting myself into, and we all appreciate that there's no time for waste. A lot of people may think out of sight is out of mind; but in my case the opposite happens. You get down to what's really important. Why look for the bad when we can look for the good? Life's too short to worry about stuff like that.'