Sir Ranulph Fiennes has conquered the Eiger and sawn off his own fingertips, but he won’t climb a ladder. Why?

Apparently not. “I hold the bottom of the ladder and send Louise [Billington, his second wife who is 24 years his junior] up to clean the leaves out because it’s three storeys,” he says in that rich and reassuring tone of his. “I know that I would be frightened up at the top.”

How, then, did Sir Ranulph cope with life on the Eiger’s dizzying rock face in winter? Kenton Cool, his guide and one of the world’s most experienced climbers, is part of the answer. “He has experience of working with people who have vertigo and making them control their minds,” Fiennes explains. The trick, he says, is never to look down – or to even think about it. “For three days and even nights on little ledges I said that constantly to myself.”

Steve Seaton, Peter James, Sara Odell and Sir Ranulph Fiennes on a glacier hike in Argentina in 1999

There was a hitch when he found himself perched precariously above a vertical 1,500-metre drop and had to look down in order to make sure his crampons were properly engaged with the tiny footholds. He had reached what’s known as the Traverse of the Gods on the north face of the Eiger and was terrified. “I wanted to retreat before the rushing noise of the vertigo made my fingers weak. You can’t afford to have weak fingers – particularly when half of them have gone on one hand,” he says, referring to the time when he sawed off the frost-bitten tips of the fingers of his left hand at home rather than wait for a surgeon to amputate. “Ginny [his first wife and childhood sweetheart who died of cancer in early 2004] brought me cups of tea. I had a proper Black & Decker workbench – bought it for the occasion – with a proper micro saw.”

Back on the Eiger, Sir Ranulph screamed at Cool, who had disappeared around a curve in the rock face, to slacken the rope. But his guide was preoccupied with securing their position at a precarious point. “To hear someone screaming at him annoyed him and I got a whole load of abuse back (and a bit of slack) and I suppose my irritation at him screaming at me like that countered the onrush of the vertigo –which is mental – and I got to the other side of that horrific bit.”

Then what? “Then you’ve still got to do it!” How? “Oh God knows, it’s probably one of the worst moments of all. In the same way as when I had my massive heart attack [he underwent a double heart bypass in 2003] I remembered nothing about it afterwards."

Don't look down

The closest parallel he can draw to this “dreadful, dreadful moment of terror” is the day he plunged into the Moran Canyon on the thundering Fraser River in British Columbia in a rubber boat. It was 1971 and the only people who had tried it before were two French canoeists who ended up on a mortuary slab. “The moment of letting go of the bank into the incredibly fast river was equally frightening. You have to say ‘Go, go, go!’ It’s a moment and you’ve got to go ‘bang’, like hitting a table with your fist.”

At Eton, the young Fiennes would sneak off after lights out and climb local buildings. Because he couldn’t see down in the dark, he didn’t get vertigo. But while he was training with the SAS he was instructed to keep his eyes open on parachute jumps to avoid tangling with fellow jumpers. “As soon as I fell out I closed them until the parachute opened, which would have been a sackable offence,” he admits.

Since his Eiger experience in 2007, Sir Ranulph has given up on overcoming his fear of heights. “When I got to the top – with huge relief – I knew that if I hadn’t lost my fear of heights on that climb then I never would. So I made up my mind: all future expeditions would be horizontal.”

But, hang on. Everest [which he climbed at the third attempt in 2009] is hardly horizontal! “Well, there aren’t any drops,” he says. Seriously? “On the Hillary Step there’s a drop but you do that at night. You look down anywhere else and there’s a sort of white slope, not a drop.” Clearly, conquering fear is a case of mind over matter. And that attitude will come in handy for his next challenge. At the age of 72, Sir Ranulph is now attempting to become the first person to cross both polar ice caps and climb the highest mountain on each continent, in aid of Marie Curie Cancer Care.

Prince Charles and Sir Ranulph Fiennes

Sir Ranulph’s life story reads like fiction. There was the time he shot a soldier while seconded by the British Army to fight for the Omani government in the late 60s. “We were setting up an ambush, as instructed by my commanding officer, and I said: ‘Put your hands up.’ The soldier swung his Kalashnikov round and in that brief half second I was extremely frightened. That’s why I shot him.”

Fear, as you might expect, doesn’t play much of a role in Sir Ranulph’s day-to-day life. “I like to be in control,” he says. He’s now written a book exploring the psychology of fear and interviewed people who he says have experienced fear far worse than he ever has.

His own recipe for overcoming fear sounds straightforward: avoid it. On expeditions, he says, “the key thing is to avoid risk and therefore avoid fear. So when there are polar bears around you want to have a gun. It’s only when I’ve been in an area with polar bears with no gun that I’ve felt frightened.”

His advice to the rest of us? “Find out exactly what you’re frightened of and try and get away from that situation so it doesn’t exist any more.” As self-help goes, it’s at least a little more pragmatic than Roosevelt’s exhortation to the American people during his inaugural address. As the president said: “The only thing we have to fear is fear itself.”

Buy Fiennes' book, Fear: Our Ultimate Challenge, for £16.90 from the RT bookshop

Book of the Week: Fear is also on Radio 4 Monday-Friday at 9.45am