In 1975, Doug Scott survived what was considered impossible: an unplanned night out below the summit of Mt Everest. On paper, he was doomed. Was he worried? 

 "No. I was fine with that."
To recap: Scott and Dougal Haston had just conducted the technically draining first ascent of Everest by the 'sharp end' - the notorious south-west face. Their summit photos were drenched in sunset: a sight nobody ever wants to see on Everest. They had no tent. No oxygen. Light clothing. It was -30 deg C. It would be the highest bivouac ever attempted and the first time humans would endure a night at that altitude without oxygen. Their unscathed survival would heft the bar for what it was believed people can endure. Clearly, how this could be considered 'fine' on the day was a question worth asking. This was the answer.

"When I was 19, I was on Bidean nam Bian, in Glen Coe. We got hit by a winter storm. In the end we were forced to spend the night on the summit. We made something like a car bonnet from snow, and got our legs into that. We only had very light clothing, and just sat there in this little igloo for 14 hours. It's experiences like that which gave me the confidence to not think too badly about spending the night on Everest." Wind chimes fill a brief silence. "Scotland can be pretty mean in winter."

Doug Scott has a comprehensive knowledge of exactly where the limits lie in the mountains. He's spent his life finding them, kicking them aside, and drawing them a new line in the snow. His mantra is a first-century quote by Cicerone: "The thing that fascinates man most is the unknown". You suspect that working outside of the shadow of others' experience would be frightening, but doing-what-the-other-guy-ain't has always been Scott's drive, his confidence escalating with each step into the unknown. After all, if nobody has done it, nobody can tell you it can't be done.

And so it went. Twenty first ascents. Climbing 40 major peaks in lean, stripped-down 'Alpine' style. All Seven Summits - the highest peak on each continent - mostly by new routes. Over a career as Britain's most pioneering mountaineer, he's also built a reputation as its toughest fighter, not only surviving, but triumphing in the face of seemingly hopeless odds. And today, as a highly effective humanitarian crusader, Doug Scott is still fighting.

Barring an impressive picture of Scott victorious atop Everest (which hangs in the bathroom) and the fact that the chap sawing wood on the drive happens to be ace climber Leo Houlding's dad, there's little to suggest whose house this is. This serene Lakeland garden is a monument to peace and quiet. Tibetan chimes tinkle. And the sturdy, slightly bookish gentleman sitting on the bench doesn't look like the chap who for 30 years was the rascal-haired technical muscle of British exploratory mountaineering. Who was the first British person on Everest. Who broke both legs beneath the summit of one of the world's hardest mountains - then crawled down it. Who has shared ropes with Messner, Bonington, Haston, Whillans, Boardman, Tasker. Then he shakes your hand and fixes you with eyes like the Hindu Kush - and you see it.

Doug Scott - CBE - is 67. The wilful hair and beard have gone, and besides his nutcracker handshake and a slightly stiff walk, few physical clues as to his life of gruelling physicality remain. According to friends he is still quite the athlete: he climbs, displaying impressive fluidity when placed on anything vertical. He is quiet, but unreserved in his opinions. To have someone of his experience around to share thoughts is rare: of his contemporaries who pushed mountaineering limits through the Seventies and Eighties, he's one of the few who made it home.

The climb Scott considers his most significant turns 30 this year: the first ascent of Kangchenjunga, the world's third highest mountain, by its north ridge. "I saw Kangch from Everest in 1975, and I'd always admired the way it had first been climbed. In 1955 I knew of the 'Human Fly', Joe Brown, doing Cenotaph Corner in Snowdonia. Then suddenly here he was doing hand-jams at 28,000ft on Kangchenjunga. At 14, that impressed me. But I never thought I'd be up there to see the actual crag."

Scott's ascent would be a triumphant coalescence of all aspects of the climbing style he had pioneered: a stripped-down, oxygen-free ascent of a big mountain by a new route, via the application of experience, guts and the 'sixth sense' Scott makes repeated references to. Like all of his major ascents, it was virgin ground. "I couldn't think of going all the way to the Himalaya just to keep repeating what others had already done. To this day, on all the 8000m peaks - Everest aside - there are major features still unattempted. Features which really do catch the eye, and draw you to them."

So it was with Kangchenjunga's north ridge, and not just the route. "There was more uncertainty on that climb than others I've done. We didn't take any oxygen, just one bottle for emergencies, which we lost. What if one of us stepped too far? Got an edema? I had no idea how I would cope."

With Pete Boardman, Joe Tasker and Georges Bettembourg, Scott's team numbered just four. "It was very interesting. This is the thing of climbing new routes: wondering what is round the next corner, that next bulge of rock and ice, through that rock band, how you'll be up there. So fascinating."   

But not easy. Beaten back for a second time, the climbers sat despondent in a snow cave at 25,500ft.

"Georges decided he didn't trust the weather.
We sat there asking ourselves 'if we were the last people on the planet, would we be up here, doing this?' No we wouldn't. It had been a hell of a stormy two months and home comforts were definitely winning out. But then we thought how people back home had put themselves out for us."

In the end the choice was made for them. "When you're pushing yourself to the limit of your endurance you do seem to access areas of your being which are normally hidden. But there are times when I've almost been told what to do next.

 "I awoke at 3am with a feeling, like a voice in my chest, telling me I should go straight back up. Not go back to the col for supplies: just go straight for the top. It was such a strong feeling that I couldn't go back to sleep. I put the stove on, moved the block away from the cave door and was startled to find a beautiful starlit morning. No wind."

Not all were convinced. "I woke the others and foolishly said: 'I've just been visited!'," he chuckles. "Joe had spent seven years in a Jesuit seminary and had left that sort of thing behind, so told me what I could do with that. But Pete got interested when he saw how calm the morning was. So we set off, and next day we made the summit. Or ten feet from it."

Stopping short of the summit was in deference to the Sikkim people, who regarded it as sacred. It was finally desecrated in 1980 by the Japanese, who trod all over it. "It would have been great if one major mountain had remained untrodden." 

Phrases like "a calming prescience", "sixth sense", and "inner voice" augment Scott's philosophical demeanour, and his serene acceptance of the influence of spirituality on even his most technical ascents. Has this attitude always been present? "I probably became more aware of it the older I got. I was pretty gung-ho in my twenties."

Before he was gung-ho, Scott could barely be called interested. He recalls the occasion when, in the Royal Albert Hall, he was given a clout by his teacher and told sharply to behave during a talk by John Hunt, leader of the victorious 1953 Everest expedition. "I had absolutely no interest in Everest, or anything like it. I'd rather be out there myself."

He started climbing aged 12, on the Black Rocks in Derbyshire, and recalls arriving at the crags with his mother's washing line. Day climbs turned into camping trips, and soon Scott started getting interested in other places. "By 1958 we started heading off to Chamonix and the Dolomites. It was all very exploratory. Climbing was seen as quite eccentric in those days." The Alpine trips would be the first steps that would take Scott - then a geography teacher - progressively higher. "We were working up, with trips to the High Atlas, Turkey, Chad. Then we decided to go for something bigger."

'Bigger' was the Hindu Kush in 1967, for alpine-style winter first ascents on 6000m peaks. "I found I could cope with the lack of oxygen, and started to look forward to going to Nepal. But for five years my domestic situation was such that I couldn't get away. So I mostly got stuck in to big wall climbing."

Stints in Yosemite, unscaled walls on Baffin Island and Scotland followed. Then, in 1972, the call came.
"Don Whillans rang me up and asked me if I wanted to go to Everest. I said 'yes, when?' and he said 'three weeks'." Led by Chris Bonington, the expedition comprised the cream of British mountaineering: Hamish MacInnes, Dougal Haston, Don Whillans and, now, Scott. Forced back by vicious winds at 8300m, the technical difficulties encountered served to highlight just how hard an ascent of Everest by its south-west face would be. In 1975, they tried again - successfully.

Scott fondly remembers the liberating final push.
"Beyond Camp Six the climb immediately had a very different feel, just Dougal and myself, no fixed ropes, more and more absorbed in the next step. We were completely in the moment, moment after moment, all day, with a calm prescience that we'd make it. It's a wonderful feeling when you're out on a limb like that, going for it, your trust in the lap of the gods. It's very exhilarating. And we got it right."

The pair reached the summit of 'Big E' at sunset on 24 September 1975. After trying briefly to descend, they began to dig a snow cave - resigned to spending the night feet below the top of the world's highest mountain. "It was under control." Scott pauses. "Just." Others had bivvied on the mountain lower down, all suffering awful frostbite. Scott passed the night massaging his feet and obsessively enlarging the cave until it was big enough to sleep four. "The quality of survival was good."

It's no surprise given his experiences that Scott has developed a robust rationale when it comes to risky ascents. "Intuition is the distillation of experience. This thing of deserving to be up there having served your apprenticeship is pretty important if you're going to wait for intuition to kick in - for that sixth sense to tell you whether you're going to carry on or pull out. If ambition blinkers your intuition, you can get yourself into trouble."

 'Trouble' could describe one incident in 1977, just below the summit of Baintha Brakk - aka The Ogre. This 7285m snarl of rock in Pakistan is one of the hardest mountains in the world. Moments after completing its first ascent with Chris Bonington, Scott slipped and shattered both legs at the ankle.
"It was a case of being too gung-ho. I was at the point where I was standing at the bottom, looking at the summit and thinking to myself 'I'm going to get from here to there…' not quite 'if it kills me', but along those lines. Which was really stupid. Of course, it very nearly did kill me. And Chris."
The descent was hell: an eight-day crawl over complex, frozen ground, jarring Scott's broken legs with each shuffle. Starvation followed a further setback when Bonington broke ribs and developed pneumonia. Surely this time survival was doubtful?

"Not exactly, no. It was just in control. The five-day storm was something else, but with the help of Mo Anthione and Clive Rowland [fellow members of the expedition], we were able to cope. I realised that there were new rules for winning, then took it one feature at a time: one rock, one pinnacle, then deal with the next one. It happened at 24,000ft: base camp was at 12,000ft." He pauses. "To think about the whole thing was mind-boggling."
Perhaps a lot of people might have given up?
"No. Everyone wants to get home. When people say 'only you could have done it'… that's nonsense." Another pause. "We all want to get home."

Amid the tragedies that ravaged British mountaineering through Scott's decades of activity, many friends didn't. Boardman and Tasker died on Everest, Al Rouse on K2, Alex MacIntyre on Annapurna, and Dougal Haston in an avalanche while skiing. Did he ever come close to quitting?
"No. People did say, 'how can you keep going, you callous bastard, when all of your mates are dying?' I became quite fatalistic. Of the 12 good friends I lost, they all had someone close to them who'd had a premonition it was going to happen. Maybe it's all mapped out beforehand. Plus, you never think it will happen to you. So I kept going, despite the huge sadness that these lads weren't around."

Scott still climbs, often with fellow survivor Bonington, who lives minutes away. But as regards the really serious stuff, he knew when to stop.
"The last new thing I did was in Nepal, the south pillar of Drohmo, in 1998. A fine, elegant pillar. I'd seen it winking at me from Kangchenjunga, and did it in four days, very slowly. I was coming to the end then. The end is marked by your inability to carry your share of the load. That's time to call it a day."

But Scott is still pushing. Always simmering during his climbing days, his concern for the welfare of the Nepalese people who have helped his expeditions so much has hit furious boil.

Building on the ethics of the late Mike Cheney's Sherpa Cooperative - a trekking company that piled profit into porter welfare - in 1989, Scott started Community Action Treks (www.catreks.com).
" The Nepalese have hardly any of the amenities we take for granted. And yet they do everything with a huge smile on their face. It seemed appalling to me, after all Sherpas and porters have done to send us back with the best possible impression of their country, for us to not give them the same medical care, or to pay them a decent wage. Some supposedly top trekking companies still pay inhuman wages to porters via agencies."  

 In 1990 while in Pakistan, Scott became aware of the mortality rates of infants in Askole from contaminated water supplies - some 50 per cent. He was able to organise a clean water supply to the town, which cut this death rate dramatically.
Just like his climbing, the bar was raised by this success. Today CAT's charity wing, Community Action Nepal (www.canepal.com) raises money through talks, fairs and donations. "We build rescue posts, schools, sanitation… some 40 projects in the middle hills," he says with pride, his typically fleeting eye contact steady. "Some porters are left to fend for themselves when they have edema, many die. We've just built a rescue shelter in Khumbu region. Next year it will be staffed by specialist doctors."

Some might see Scott's greatest achievement as surviving his own life: but this latest challenge stands as his toughest. Some may say it can't be done. But if his climbing career is anything to go by, this will only make him try harder. And achieving the impossible is something this man knows a fair bit about.