There's a boundless enthusiasm about Brian Blessed, as he welcomes me into his Surrey home, introducing me to his wife and dog before venturing into a cabin in the garden, where our interview takes place.

His voice and broad frame are still hugely powerful, his language colourful, his anecdotes delivered in a variety of accents, long bushy beard moving up and down as he speaks, eyes almost popping with excitement. Like a lion, he roars through life, both vocally and physically.

The cabin is an Aladdin's cave of clutter, peppered with personal mementoes. There are pictures of Everest, a signed photograph of Buzz Aldrin, a variety of buddhas, Sri Lankan elephant statues and a recent contemporary portrait of himself laughing, created by a leading artist in Nepal.

Blessed, 79, barely pauses for breath as he recalls the people he's worked with, from Peter O'Toole to Katharine Hepburn, his escapades on Z-Cars, Flash Gordon and Star Wars, his early years as an undertaker, his three Everest missions and his friendship with Kenneth Branagh, who happens to live up the road.

It's fitting that his memoir is called Absolute Pandemonium, because it's written not in any particular chronological order, his boisterous self bounding out of every page.

Indeed, he asks people to read it with his voice in mind and admits his thoughts are spontaneous, making for a very entertaining and somewhat chaotic read.

"I want to leap out of the pages at you! Not literally, of course. I mean, where on earth would you keep me? I'm quite a size."

In the two hours I'm with him, I am able to ask about five questions, and that's not without raising my voice to try to interrupt him, frequently unsuccessfully. When Blessed is on a roll, he's like a runaway train.

He talks about O'Toole at length, how wonderful and awful he could be, a 'Jekyll and Hyde' alcoholic of whom other actors were petrified - but not Blessed.

"I stood up to his violence. I'd been a champion boxer and judo expert. I'd always been tough. I'm not frightened of anything. From the first time I met O'Toole, I loved him on sight, but there was an antagonism as well. I've never met anyone who observed acting so well and we challenged each other."

Katharine Hepburn is another favourite topic. They met in 1971 on the set of The Trojan Women and were to have a close relationship for many years.

"I don't like words like platonic or organic - it was a very deep friendship. We didn't make love but we kissed and we held each other. I didn't make the final move in the end. I didn't feel anything about me being 31 and she being 61.

"I think we would have gone on, but there was too much pressure from so-called associates and friends."

Even David Cameron features in the book, for asking him to say his famous catchphrase outside Number 10 when Blessed visited Downing Street for an event. He booms, "Gordon's Alive!", Prince Vultan's famous line, joyously reliving the Flash Gordon moment.

Born in Mexborough, Yorkshire, the son of a coal miner, Blessed had to leave school at 15 to earn a wage, after his father shattered his hips in a mining accident. He became an undertaker's assistant, making coffins and dealing with corpses (there's a hilarious chapter on this), before embarking on an acting career and, after national service, joined Bristol Old Vic Theatre School.

While he has appeared with the great and the good on both TV and in the theatre, adventure has played an equally important part in his life.

At 57, Blessed became the oldest man to reach heights of over 28,000ft without oxygen, and is also the oldest man to reach the magnetic North Pole on foot. He has climbed Everest three times, but never reached the summit.

"I have a gift for altitude. To go at almost 60 years of age to 400ft below the summit of Everest without oxygen is unheard of. I have lungs twice the normal size."

He's once again planning another expedition, despite having to pull out of King Lear in January on the advice of his doctor, after collapsing on stage.

But he plays down this frightening event.

"I just had to stop because part of my machine [pointing to his heart] didn't work for a few days. It was slight fibrillation because of my many times at altitude. No human being has gone to high altitudes so many times at such an old age. You pay a price for that.

"My big expeditions started when I was around 55, when many people are thinking of retiring," he adds. "So a part of my heart gave me a bit of fibrillation. I wanted the best heart specialist on it, not out of vanity, but because of the things I want to do."

He's had a pacemaker fitted and is once again raring to go.

"Within minutes, they said, 'Your heart is now 100%, you have the heart of a 30-year-old'. I have tests all the time. They say I have a massively powerful heart.

"Now I'm bench-pressing, doing weights and planning all my expeditions. I am cured! I want to go to the South Pole, I want to go into space, I want to go to the moon.

"The doctors say, 'Shall we speed up your heart machine? I think we can speed it up slightly when you go to Everest, Brian. Maybe we can come to Everest base camp and then we can tune you'."

He has never let age interfere with his ambitions.

"I think that 40 is incredibly young. Middle-age is between 55 and 65. It's not how old you are, it's how you are old. When my father was 99, I said, 'Dad, what's it like being old?' He said, 'I don't know what you mean. I'm the same now as when I was a child'.

"And regards death, you can give it a healthy 'V' sign. Death doesn't exist. You have always been alive. Life is the last word, death is not. I have no fear of anything.

"I run between five to 10 miles a day and I have my own rough gym, with rocks in sacks. I don't have all that modern s***. I'm always ready to go."

He meditates for half an hour every morning and evening too, and loves being on his own in the wilderness, whether it's in the countryside or up a mountain.

"People ask me, 'Is it not dangerous going up Everest or the North Pole?' I say, the greatest danger in life is not taking the adventure. When I'm 80, I want to climb Everest to raise money for Nepal."

He has been married to the actress Hildegarde Neil for 37 years, with whom he has a daughter, Rosalind, who's also an actress. His wife does not, however, like him going on dangerous expeditions, he admits.

"My wife is very practical. She's very emotional but she wouldn't stop me doing what I want to do. She doesn't quite understand why I'm doing it but I think she secretly admires it."

In the next year, he hopes to do King Lear again and direct several plays - as well as fitting in a spring expedition. He's keen to go in search of yetis in Canada, Russia and Malaysia. Indeed, he has so much more life to live.

Blessed aims to take Katharine Hepburn's advice, which he recounts: "Always try and say 'yes' to life, Brian. And don't obey all the rules. If you obey all the rules, you miss all the fun."

:: Absolute Pandemonium by Brian Blessed is published by Sidgwick & Jackson, priced £20. Available now