Sir Ranulph Fiennes

Seven days, seven continents, seven marathons - an awesome test for any athlete, let alone one getting over open-heart surgery and preparing to draw his pension. But to Sir Ranulph, such unprecedented endeavour is "all good fun really".

The physical toil, dehydration and jet lag of such an errand will all take their toil on the body of Sir Ranulph who, only 16 weeks ago, underwent bypass surgery after a heart attack on a plane.

He was placed on a life support machine, and while he recovered was told not to exercise for two months. Nevertheless, the explorer was back jogging within a fortnight of his operation and, a month ago, ran his first marathon since leaving hospital.

The marathon man in action

After marathon number four - in Singapore - he admitted it had been a mistake to begin the whole venture so shortly after his illness. And his co-runner, Dr Mike Stroud, had medical difficulties there that forced him to walk part of the distance. Both carried on regardless.

Sir Ranulph believes that "the bypass has slowed me down enormously" but, in fact, doctors have estimated that the surgery may actually have helped his heart's performance by clearing his arteries.

Following his treatment at the Bristol Royal Infirmary, the charitable beneficiary of this extended jog is the British Heart Foundation.

This is only the latest challenge for the man described in the Guinness Book of Records as "the world's greatest living explorer". The Prince of Wales has said that, without the adventures of Sir Ranulph, the world would be a duller place.

He made his name in 1982, with a global trek that covered 35,000 miles and extended to both poles. He was the first explorer to cross the Antarctic unsupported, and helped unearth the lost city of Ubar in southern Oman.

He has faced starvation, suffered frostbite in his fingers and gangrene in his foot. Only a ski strap saved his life when he once fell over the edge of a polar crevasse, and he has abandoned far more expeditions than he has completed.

But the famously sanguine Sir Ranulph assesses his personal risk as no greater than those of "a salesman, for instance, driving up and down the motorway". He makes his trips into the wilderness, often alone, simply because "it's my profession, it's what I do".

SAS survival skills

Sir Ranulph Twistleton-Wykeham Fiennes, an aristocrat whose lineage can be traced back to Charlemagne, originally opted for an Army career. His father had died four months before his birth, and Sir Ranulph wished to follow him in leading a Scottish regiment.

Fiennes and Stroud: Together against the elements

However, his poor academic record prevented his going up the ranks, and he had to settle instead for a series of commissions.

A stint with the UK's elite regiment, the Special Air Service or SAS, taught him the survival skills that would later serve him so well. But he had to leave the unit after purloining some gelignite to blow up the Dr Doolittle film set in a Wiltshire village.

If all this sounds straight from the pages of Boys' Own, Sir Ranulph undercuts such heroics with his upbeat approach to his work.

His sometimes desperate attempts to survive his battles with the elements do little to make him delve deep into his psyche, and radio psychiatrist Dr Anthony Clare once likened interviewing him to "stirring a void with a teaspoon".

Footsteps of Captain Scott

Sir Ranulph favours pragmatism over romance when discussing his endeavours, which he calls merely "a way of paying the bills". By way of explaining his journeys to the outer reaches, he says, "my publishers don't want to hear about an expedition to Primrose Hill".

His books about his travels and best-selling novels certainly keep him in hiking boots and, for extra pocket money, there are promotional tours and lucrative speaking engagements.

His most recent work is a biography of Captain Scott. Of his research into his polar predecessor, Sir Ranulph says, "If you're going to write about hell, it helps if you've actually been there."

This week, to the rest of us it looks like he's been paying another visit.

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