PEN HADOW, somehow incongruous in a suit rather than a fur and ice-fringed polar parka, wriggles even deeper into the battered old sofa in the library at his beloved Royal Geographical Society (RGS).

He’s travelled from his home on Dartmoor to London to give a talk about his trek to the South Pole with Simon Murray and to promote Solo, his book about how, in the spring of 2003, he became the first person to walk (and, several times, swim) alone and unsupported to the North Pole.

His discomfort is because I have asked him the question that all adventurers dread: why? What drew him to the Pole and why return after two previous failed attempts, either of which could have ended in his death? Hadow is a man who has a clear idea of his responsibilities — to his family, to the community and, pragmatically, to the media whose interest in his adventures has, he concedes, created his public profile. He is, however, a private man, not keen on exposing his inner workings. Hence the squirming. The Times has sent me to quiz Hadow because, after two (failed) expeditions to row across the Atlantic, I am thought to be better placed than most to find out what drives such a man for a third attempt.

I’m not so sure. My own adventuring is partly about a need to prop up my own sense of self-worth and designing my own, unique challenge, safe in the knowledge that, succeed or fail, it and I will remain essentially an enigma and, therefore, beyond normal judgments of success and failure.

Hadow considers this and then says: “Well, there is some merit in that, but it’s not the whole story.

“There is a cocktail of motivational forces at work, evolved from experiences you have had in your life and maybe some genetics — but when push comes to shove, you do it for yourself. There is a part of me that does it for other people, so I did it for my father, up to a point, I did it for the family name, up to a point . . .”

Certainly the past has played a big role in shaping Hadow. One forebear, Douglas Hadow, took part in the catastrophic first ascent of the Matterhorn, in 1865. The 19-year-old was thought to have lost his footing and dragged three others with him to their deaths. In 1878, Hadow’s great great-grandfather, Patrick, chairman of P&O, won the second All-England tennis singles championship.

That Hadow grew up playing hardball with himself is hardly surprising: from an early age he set out to test himself. At eight, his mother found him hanging upside down by his legs from the branch of a tree. She feared he had been killed, whereas: “I’d been hanging upside down by way of an experiment to see how long I could last”. The answer? At least four hours.

But central to Hadow’s driving force was his relationship with his father, Nigel, a man he adored but who was a misfit in the world of work. “He had a lot of interests and skills and was talented, but neither he nor the people around him were able to harness it. He was fantastic and an inspiration but not in how to build a career and make your way in the world.”

So he was a failure?

“No, because your ultimate responsibility is to be a father and a husband and he was ahead of his time in the way he interacted with us. But I overreacted in that it motivated me to aspire to be at the top of any tree into which I put myself.”

The paradox, of course, is that for Hadow, his chosen path means that he is often absent from his wife, Mary, and children, Wilf, 6, and Freya, 2. He is aware of their sacrifices but believes that they gain because, at peace with himself, he emerges as a better husband and father. “When Mary married me I was already doing this stuff. She realised that if she tried to change me that would be the end of me as the person she loved. I have needed her support. I can’t imagine doing any of this without her.”

Physical and mental endurance proved to be Hadow’s métier, but at first it looked as though he might go the way of his father. He signed up with IMG, Mark McCormack’s sports management company, as its youngest executive, but he realised that he was never going to be happy assisting others to fulfil their dreams.