EXMOOR explorer 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 (4,892m) peak.

He is halfway to completing the Global Reach Challenge in aid of Marie Curie, having already crossed both polar ice caps and and climbed Mount Everest in Asia, Mount Kilimanjaro in Africa and Mount Elbrus in Europe.

To achieve the world first, he still needs to summit Mount Vinson, Aconcagua in South America, Mount Carstensz in Australasia and Denali, the highest peak in North America.

Sir Ranulph, who has suffered two heart attacks and undergone a double heart bypass, has vertigo and a breathing condition called Cheyne-Stokes while climbing.

Speaking about the imminent climb, the veteran explorer admitted he was nervous but pledged to continue for as long as possible.

"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 raised will help the charity provide care and support to people living with a terminal illness and their families.

He described the work of those who work for 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 though 'this is wonderful' and in knowing them I learnt that they only cover certain areas of the UK.

"If you're in the wrong area of the UK you're going to miss out on the possibility of these wonderful angels.

"In order to get more, we need money to train them and this particular expedition, if it succeeds, will train at least 55 nurses."

Sir Ranulph has raised £18 million in total for charity and aims to raise £20 million for good causes in his lifetime.

In 2009, he was the first person to cross both ice caps and reach the summit of Everest.

And he circumnavigated the world on its polar axis during a three-year expedition travelling solely by sea and lane in 1982.

Dr Jane Collins, chief executive of Marie Curie, said: "Sir Ranulph has an unfailing commitment to raise money for Marie Curie and he is quite literally going to the ends of the earth and back to do so.

"His determination and ability to push himself to his limits is truly inspiring.

"We hope Sir Ranulph will inspire others to take on their own personal challenge in aid of Marie Curie and help us care for more people living with a terminal illness."

Paul Sykes, long-time benefactor of Sir Ranulph Fiennes, added: "Sir Ranulph proves with enormous willpower what can be physically achieved. He is a friend and hero to me and I am proud to support his latest endurance challenge."

Frederik van Tuyll, chief executive of the TMF group which is sponsoring the challenge, described Sir Ranulph as "the world's greatest living explorer".

"He has inspired many for generations with his perseverance and dedication, and has pushed himself to the extreme to complete some of the world's most gruelling and difficult challenges," he said.

"He has shown that to succeed in remote areas requires not only tremendous ambition but also detailed local knowledge and expertise - so he surrounds himself with a strong team, all experts in their field.

To support Sir Ranulph's Global Reach Challenge in aid of Marie Curie, go to www.justgiving.com/Ranulph.