The pair hope to raise at least £2.2m for Marie Curie's Delivering Choice programme, which allows terminally ill patients to choose where they spend the end of their lives.

Marie Curie has warned that without £6m over the next three years it cannot afford to extend the scheme beyond its seven current pilot projects around the country.

Mr Sykes, who previously backed Sir Ranulph on expeditions to Everest and the Eiger, said: "I don't give money away, I invest it." He said Marie Curie was a fantastic charity with some wonderful people. "It's a privilege to be working with them.

"I can't think of a more important gift that you can give somebody at the end of their lives than to give them the chance to go home."

The last time Sir Ranulph, 64, made an attempt on Everest was in 2005, only two years after he suffered a heart attack.

After 72 days on the mountain he was less than 500 metres from the 29,000ft summit when he experienced excruciating chest pains and had to turn back.

This time he will be under the guidance of Himalayan guide Kenton Cool, who successfully led him up the sheer icy face of the Eiger last year.

Sir Ranulph says Marie Curie is a charity close to his heart after losing his wife, two of his sisters and his mother to cancer and also having what he describes as "a brush" with prostate cancer.

He said: "Marie Curie nurses don't grow on trees. What Paul and I want to do is increase the ability of Marie Curie to extend their services to many more people."

Thomas Hughes-Hallett, chief executive of Marie Curie Cancer Care, said Sir Ranulph's support was invaluable. He said: "As we don't spend money on advertising and spend every single penny we raise on nursing care, we need people like Sir Ran to raise our profile.

"That a man like him can go and do something like that is extraordinary. It's also very inspiring for the rest of us – if that's what he can do, what can we do?"