Sir Ranulph Fiennes’s plan to climb Mount Everest, three years after his previous assault on the summit, could kill him, doctors and his wife believe.

The record-breaking explorer, who nearly died in 2005 when he collapsed 300 metres from his goal, admitted yesterday that he had not convinced his wife, Louise, that he was being responsible — but he was going anyway.

“My wife is not keen on the expedition at all,” he said. “I think she reckons that my health is not good enough to do it. I disagree. I think it is good enough. Louise has not been able to stop me from going.” The venture aims to raise £3 million for Marie Curie Cancer Care. Sir Ranulph’s first wife, sister and mother died of cancer within 18 months of each other.

Sir Ranulph, 64, had allowed his first wife, Ginny, to restrict his adventures to low-altitude expeditions, but today no one could deter him, he said. “I don’t like being driven by my wife, or by the memory of my late wife. They knew when they married me that I was an explorer. If they wanted to marry a person who stayed at home, then they should have married someone else.”

Heart specialists contacted by The Times confirmed that Mrs Fiennes’s fears are well-founded. Adam Fitzpatrick, a consultant cardiologist and a lecturer at Manchester University, said that Sir Ranulph’s history of heart attacks made him vulnerable to a fatal cardiac arrest. “Even with heart attacks when the situation is salvaged promptly there is usually damage to the heart muscle,” he said. “The tubes could all be in good shape, but where you have healthy tissue abutting scar tissue the electrical patterns around those areas can be abnormal.”

The lack of oxygen and extreme cold were likely to cause the explorer’s heart to beat irregularly, causing a life-threatening attack, he said. “He is being a bit unwise. I would have thought that the risks were significantly greater than for a man who didn’t have his history.”

Sir Ranulph had a double heart bypass in 2003 after suffering a heart attack while sitting in an aircraft at Bristol airport. During the operation his heart had to be restarted 13 times. Nick Brooks, a consultant cardiologist at University Hospital of South Manchester, said that the risk depended on the damage to his heart: “In the best-case scenario it is risky but not dangerous, but in the worst-case scenario it is downright reckless.”

Sir Ranulph, who will be accompanied by a doctor, said that every married explorer had to overcome or defy their spouse’s concerns. He found the idea of retirement from exploration repellent, he said. “If I don’t have an expedition planned I’m like a ship without a rudder.”

Mrs Fiennes, 41, has previously expressed concern that her husband had survived through luck rather than judgment. Speaking about her husband’s previous attempt to climb Everest, she had nevertheless conceded that it would be unrealistic to expect him to give up exploring. “I wouldn’t have entertained a relationship with a man aged 60 expecting him to change,” she said.

If he succeeds, Sir Ranulph would be the first man to cross both ice caps via both Poles and to scale the world’s highest mountain. The expedition departs for Nepal next Wednesday.

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