Sir Ranulph Fiennes will this week set off to climb Mount Vinson, the highest peak in Antarctica.
The climb is part of his pursuit to become the first person to have crossed both polar ice caps and scale the highest mountain on each continent.
Despite ailing health, the 72-year-old will contend with minus 40C temperatures and severe winds in his bid to conquer the 16,050ft peak.
He is half-way to completing the Global Reach Challenge in aid of Marie Curie, having already crossed both polar ice caps and climbed Mount Everest in Asia, Mount Kilimanjaro in Africa and Mount Elbrus in Russia, the highest peak in Europe.
To achieve the world first, he still needs to reach the summit of Mount Vinson, plus Aconcagua in Argentina, South America, Mount Carstensz in Indonesia, for Australasia and Denali, Alaska, the highest peak in North America.
Sir Ranulph, who has had two heart attacks and undergone a double heart bypass, has vertigo and a breathing condition called Cheyne-Stokes which affects him while climbing.
Speaking about the imminent climb, the veteran explorer admitted he was nervous but pledged to continue.
“I’m nervous, this is going to be a difficult mountain for me,” he said.
“I’ve been training on Snowdonia, but you just don’t know what you might face and this mountain is very remote so it’s not so easy to get help if you find yourself in trouble.
“I’m pretty sure I could have done these four mountains even five years ago but it’s just possible that altitude and so on might have a bad effect now. All I can say is that I’ll do as much as I possibly can and only turn back if the guides refuse to carry on.
“I might be slow but I keep going. The trouble with the big mountains is that they can turn you back rather like the camels in the desert.”
Sir Ranulph has been raising funds for Marie Curie since the death of his first wife, Ginny, in 2004. The money will help the charity provide care to people with terminal illnesses.
He described the work of Marie Curie as vital and highlighted the importance of having someone trusted to care for a loved one.
“I didn’t really know about all that until my wife of 38 years was dying of cancer and that is how I got to know the Marie Curie nurses,” he said.
“As I got to know them I thought, ‘This is wonderful’ and in knowing them I learnt that they only cover certain areas of the UK.”