From Everest, Mont Blanc, Annapurna and the Eiger to . . . the Little Sugar Loaf. Arminta Wallacejoins world-famous mountaineer Chris Bonington for a stroll up memory lane in Co Wicklow

They look just like any group of hillwalkers, huddled in the forecourt of the Shell service station on the south-facing side of the N11 in Kilmacanogue, Co Wicklow, shuffling from one foot to the other. But they're not just any group: these are people who have been invited to scale the Little Sugar Loaf in the company of none other than Chris Bonington, who has scaled Mount Everest twice and is one of the most highly respected mountaineers in the business.

Okay, you're chuckling now. Aren't you? I have to confess I chuckled too. The Little Sugar Loaf, for goodness sake! Granted, it's a delightful walk; a line of rocky hummocks with fantastic views of Bray and the Wicklow coast. It's less than 342 metres high, perfect for those of us who pale at the mention of picks and cringe at the word "crampon". Surely, though, it's not the sort of peak that would be of interest to Sir Christian John Storey Bonington, who has bagged not only Everest but also Annapurna, Nuptse, Mont Blanc, the north face of the Eiger and the Old Man of Hoy, as well as notching up three first ascents in Greenland and scaling the snowy heights of Mount Vinson, which, at a whopping 8,848 metres, is the highest peak in Antarctica.

But the Little Sugar Loaf has, it turns out, a special place in Bonington's affections, because it was the first mountain he ever climbed.

"Hello, I'm Chris," he says, offering a hand and a beaming smile. He has come to Dublin to give a lecture and has taken the opportunity to revisit the place where his world-beating career might be said to have started.

"My grandfather lived in Mount Merrion," he explains. "I used to visit him in the holidays. My mum was a single parent so, you know, there was always the problem of what to do with me when I wasn't at school."

One day, in the summer of 1951, he decided to take the bus to Bray and climb a mountain. Why? He smiles wryly. He doesn't remember.

"It was a long time ago," he says.

We set off at a sprightly pace, a motley band composed of PR people, a delegation from the Mountaineering Council of Ireland, and an even larger delegation from outdoor clothing store 53 Degrees North, which is opening a four-floor superstore in Blanchardstown and is sponsoring the lecture series.

It's an easy climb on one of those springy surfaces whose mixture of peat, small rocks and firmly buried stones is like walking on a giant open-air Christmas cake. Every mountain has its own character, and this one resembles a sleeping dinosaur whose stumpy tail we straggle up before merrily traversing the three rounded humps of its back.

If it's a dinosaur, though, it's of the Barney variety - chubby and benevolent. Bonington, needless to say, has met some rather more fearsome characters in his day.

"I suppose the most awful was the Ogre, which I climbed 30 years ago with Doug Scott," he says. "It's in the Karakoram and it's a climb of 24,000ft." By the time dusk arrived, Bonington, who was leading, had almost reached the top. Then Scott, who had taken off his crampons to negotiate a patch of rock, slipped on some ice in the dark and abseiled into nothingness.

"And so," declares Bonington, who clearly relishes telling the story, "you have this colossal pendulum with two broken legs - compression fractures, actually - dangling on the end of a rope."

After a great deal of wriggling and shifting, they managed to get Scott to the safety of a snow cave, where the pair waited for daylight.

"It was the coldest bivouac I think I've ever had," says Bonington. "We didn't even have down jackets with us. No food, no drink. We thought it was going to be a quick romp to the top."

This is a tale with more twists and turns than a thriller. Blizzards; another abseiling accident which gives Bonington two broken ribs to add to his partner's broken legs; five days without anything to eat; and finally, just when you think it's all over, a helicopter crash which leaves Bonington stranded in the middle of nowhere for seven days while the rest of his team, oblivious to his predicament, make their way home. It's full of pace and detail, and it's easy to see why Bonington is not only a bestselling author but one of the most sought- after speakers on the mountain lecture circuit.

Meanwhile, strung out in a higgledy-piggledy line, we're approaching the summit of the Little Sugar Loaf. In front of me there's a fearsomely technical discussion going on about some new piece of equipment - possibly, to judge by the liberal use of the terms "adhesive" and "friction", a safety harness. Behind me, two lads are strolling along as if they were walking down Grafton Street, casually comparing Mount Aconcagua, the highest peak in the Americas, with Mount Elbrus in the western Caucasus, a mere 5,642-metre slip of a slope. They are, it emerges, in the midst of a series of climbs to raise money for charity and are planning an assault on Everest next April.

At the top of the Little Sugar Loaf, Bonington isn't even out of breath. At 72 he's still a high-altitude regular, with climbs in Norway, Spain and the US - not to mention a sea-kayaking trip to the Galapagos Islands to celebrate his wife's birthday and a quick visit to Australia to see his grandchildren - marked on his calendar for 2008. For now, however, he's peering animatedly over the eastern side of the hill.

"Look at that," he says. He points to where Bray lies curled along the southern edge of Dublin Bay, dozing in the sunshine. "Magnificent. For a 15-year-old boy who has never climbed before. . . well, you can imagine the effect it had on me."

It seems like a good time to ask something I've always wondered about. What's the summit of Everest actually like? How big is it? Bonington looks around.

"Oh, it's much smaller than this," he says. "It's about the size of . . ." He indicates a circle of rocks at our feet. "A pool table, maybe. There were six of us on our team, and we all fitted - just about. But the views are truly spectacular.

"To the south, where India is, it's polluted, so there are often clouds there. But to the north, you have this view of rolling mountains, which is the Tibetan plateau. I reckon the horizon is about 200 miles away, so you can actually see the curvature of the earth."

Mesmerised by the notion, I gaze across at the cone of the Big Sugar Loaf and beyond it into a flawless blue sky. But Bonington is more interested in the summit of the day.

"Come on," he says. "I'll show you how I got up here."

And to the dismay of the PR folks, who have had no breakfast and have been hinting that it's time to hit his luncheon engagement, he sets off at a run for the final heathery hump. I scramble after him, focusing firmly on my feet but stumbling and sliding all the same.

"Oh my God," I hear Bonington call, and look up in alarm. "There's a road down there. But it's okay. It's only forestry."

We look down at the Southern Cross Road, with its clutch of industrial units and squared-off housing estates at one end and the elegant bulk of Kilruddery House at the other. He is, I sense, reluctant to leave.

"This is very moving," he says. "I really feel quite moved."

The wind whips his words away and plonks them into the sea. On my recorded version it howls in satisfyingly Everest-like fashion. We all fancy ourselves climbing Everest - or do we? In his lectures, Bonington uses his ascents of the world's highest mountain as an extended metaphor for discussion of issues such as teamwork and effective leadership. But doesn't climbing demand tough decision-making, as well? There have been a number of stories recently about climbers on Everest walking past people who are in obvious difficulties.

"Actually I think they're pretty simple," Bonington says firmly. "I think you have to help people - and that's that. I mean, the idea of walking past someone to get to the summit is completely unacceptable. To think that you would refuse to help someone who's in trouble, just because of your own selfish desire to get to the top? That's monstrous."

But then there are situations where, if you stay with someone, you may die - and that's a decision everyone, he says, has to make for themselves.

Has he ever thought he was on the point of death? He frowns. "Oh, I've thought that many times," he says. "The most recent was in Scotland, climbing with my brother Gerald. I made a mistake and shot down about 800ft. I could see the whole thing, and I really did think I was a goner."

What goes through your mind, at a time like that? Do you think, "Uh-oh, I wish I hadn't done this"?

Bonington shakes his head. "Oh, no, you don't have time for anything like that."

He pauses, then gives a rueful chortle. "I'm afraid, very selfishly, I thought, 'Is this going to hurt?' "