Sir Ranulph (Twisleton-Wykenham) Fiennes is an adventurer straight out of a Boy’s Own annual. Heralded as the world’s greatest explorer by the Guinness Book Of Records, he has discovered lost cities, run seven marathons in seven days on seven continents, conquered Everest and trotted the entire surface of the globe.

It’s rare to find a picture of him where he isn’t staring out of a fur-trimmed hood, beard frosted with ice and, even at 69, he is more likely to be seen on skis than making use of his free bus pass.

But earlier this year it looked like retirement was going to be forced upon him when he lost all the fingers on his left hand to frostbite while training for the first ever winter crossing of Antarctica. Temperatures were “only” -33C, he tells me, and he’d taken off his gloves to fix the bindings on his skis, which had become loose. In less than 20 minutes his fingers (the tips of which he had sawn off after getting frostbite on a previous expedition) were “white and dead” and he had to be flown to hospital.

A diagnosis that he was in a pre-diabetic state, which may have made him more susceptible to frostbite, did little to cheer him up. “I now have a completely different diet... it’s terrible,” he grumbles.”

Whether the loss of his fingers will put paid to his adventures remains to be seen but he hopes not. Taking things easy does not come naturally to him. “I envy people who seem totally happy with life even though they don’t seem to be doing much, but I wasn’t born that way. I have to have something on the go.”

Sir Ranulph – “Ran” as he’s known to friends – began his adventuring in the 1960s after a spell in the Army that ended with him being discharged from the SAS for blowing up a dam on a film set in the Wiltshire village of Castle Coombe (he apparently thought it looked ugly).

He had no interest in becoming an explorer, he says. All he ever wanted was to follow in the footsteps of his late father, who was Royal Commander of the Royal Scots Greys. But Sir Ranulph didn’t get the A-levels he needed to get into Sandhurst – “It was the height of the mini-skirt era and, well, concentration was hard.”

By 1969, he was leading expeditions up the White Nile. Ten years later he undertook the Transglobe Expedition with some of his former SAS cohorts, travelling 52,000 miles across the Earth’s surface. They are still the only team to have managed the feat, something he puts down to good luck.

I’m rather surprised to learn that he believes “very much” in the concept. “If you muck around in icy places and try to do things other humans haven’t done, you can’t rule out the element of luck.”

Does he have rituals or superstitions when setting off on an expedition then?

“I wouldn’t openly admit to it. But I do hedge my bets. You can’t help your blood and my grandmother was Irish.”

He estimates that around half of his expeditions have ended in failure – although his definition of the word is rather different to most people’s. “Usually we count anything less than reaching the final goal as a failure.

You might break a world record but if you don’t manage to do what you set out to do then you weren’t successful.”

He made seven separate expeditions before he finally managed to locate the lost city of Iram in the Arabian Desert in 1992 and it famously took him three attempts to reach the summit of Everest in 2009. On the first attempt he suffered heart problems and on the second his confidence was knocked by the sight of three corpses – and they were people who had been descending the mountain.

A botched expedition is never an easy pill to swallow. Aside from anything else, exploring is a costly business. “Nobody pays you for organising expeditions but they cost you money to arrange. I didn’t get paid anything for five years while I was setting up the last one to Antarctica.

So in between every expedition I have to spend a year or two either lecturing or writing a book.”

Consequently, Sir Ranulph has written dozens. The latest, which deals with adventures at the Earth’s lowest temperatures, has just come out and he’s embarked on a lecture tour to promote it.

I’d assumed his thirst for adventure came from some need to keep pushing himself, to experience ever more extreme circumstances. “If I’m honest, it’s probably more about the need to keep paying the bills,” he says, before explaining how he saves money on tour by sleeping in his car.

“A hotel can be up to £260 a night whereas the back of the car costs nothing... that’s assuming you don’t stay any later than 9am when the parking restrictions come in.”

While the need to earn a crust may continue to propel him onwards, he admits his enthusiasm for putting himself in dangerous situations is dwindling, mainly as a result of late fatherhood. His daughter Elizabeth was born seven years ago, the result of his marriage to second wife Louise Millington.

His childhood sweetheart Ginny Pepper, to whom he was devoted for nearly 40 years, died of cancer in 2004, an event the usually stoic explorer called “the worst thing that had ever happened” to him. The couple had never had children and Sir Ranulph thinks now that if they had, he may have put exploring behind him a long time ago. “You don’t realise how these things change you until it happens to you.”

Fortunately the next destination on his list is nowhere more dangerous than Brighton and Hove, where he will be promoting the new book and taking part in a post-talk Q&A with fans.

“I’m rather fond of Hove,” he remarks.

“It was the site of my most challenging early climb as a student. Hove Town Hall was very difficult, especially in the dark, but we got on to the roof in the end...”

* Sir Ranulph Fiennes will appear at the Royal Pavilion Music Room at 7pm on Tuesday, November 12, in a City Books event. Tickets £10. Call 01273 725306.

*Cold by Sir Ranulph Fiennes is published by Simon & Schuster, priced £20.