The list of gruelling challenges completed by Sir Ranulph Fiennes is unparalleled and he is justifiably described as the world’s greatest living explorer. CATHERINE BELL interviewed him, as he prepares to head off on his toughest adventure yet…

North Pole, South Pole, Everest… You name it and Sir Ranulph Fiennes has done it. He was the first man to reach both poles, the first to cross the Antarctic and Arctic oceans, the first to circumnavigate the world along its polar axis (which took three years), discovered the lost city of Ubar in Yemen, set the record for the longest unsupported polar journey in history and just three-and-a-half months after a massive heart attack, three-day coma and a double heart bypass, he achieved the first 7x7x7 (seven marathons in seven consecutive days on all seven continents). Oh, and he's climbed Everest: three times. He became the oldest Briton to reach the summit of the world's highest peak in 2009.

But all of these accomplishments pale compared to what the 68-year-old former SAS man is planning next.

Dubbed the Coldest Journey on Earth, Sir Ranulph and five other men are planning to do what no-one has ever dared to do - a trans-Antarctic winter expedition.

The 2,000-mile trip is expected to take 14 months and Sir Ranulph and his team have had to meet strict criteria set by the Foreign Office before they were given the permit for the incredibly dangerous journey.

If it was up to Sir Ranulph, he'd be skiing.

"Two of us wanted to ski across Antarctica in winter but there's no way we would ever be permitted to do that," he said. "With no rescue facilities at all, we would be in grave risk of becoming an embarrassment to our country if something went wrong. I don't see it like that but you can see why the Government does. They wouldn't want people asking 'Why did you let them do it?'

"It's not just us, every country is the same."

He added: "This is the first time it's been allowed. They wouldn't let us do it unless we ticked all their health and safety boxes. We needed a mobile base that would be self sufficient for six people for a year. That opens a whole new world of planning."

The team includes Sir Ranulph's surgeon and co-adventurer Mike Stroud, as well as two expert mechanics and two men whose job is to operate a crevasse-detection system ahead of the expedition's vehicles.

The vehicles - called cabooses - were described by Sir Ranulph as "caravans on skis". One of the crucial pieces of equipment onboard is the snow melt tank, supplied by St Ives firm SF Opal.

Sir Ranulph said: "There's no water anywhere so we have to make our own out of the snow. That means we shouldn't stop in an area of blue ice - it's much more difficult cutting ice than shovelling snow.

"In the caboose we have a very cleverly manufactured system for living. In normal temperatures everything is simple but for these conditions all the plumbing, everything, has to be on the advice of specialist engineers."

He continued: "We heard fantastic reports of a company in St Ives called SF Opal and asked them if they might be able to design and manufacture a system that we could position into our tight living arrangements."

As well setting another record, the team will be gathering vital information for organisations including NASA and the European Space Agency.

"We'll be verifying the findings from their satellites," Sir Ranulph said. "It has been done by scientists in Antarctica during the summer but has never been done on a traverse of this nature."

They will also perform experiments for universities and the pharmaceutical giant GlaxoSmithKline, who are interested in how the conditions affect nutrition and hydration.

Sir Ranulph explained that he's "not scientific" - he doesn't know how to send a text message - but uses his adventures as a valuable platform to raise millions of pounds for charity.

"Our expeditions have raised £16million for charity. The particular charity on this expedition is Seeing is Believing."

The target this time round is to raise $10million - but whatever they raise will be match-funded by the Chartered Bank of Hong Kong.

Sir Ranulph is passionate about the charity, which transforms the lives of children in the developing world.

"At the moment it costs £9 for every pair of spectacles that we give to a short-sighted child," he said. "In the UK, this doesn't have a meaning - here, we think spectacles fall from heaven but that doesn't happen everywhere. If you are short-sighted, you don't go to school - and not going to school can affect your whole existence. Therefore, by raising $10million, we're benefitting human lives in a very big way."

The Coldest Journey will also benefit youngsters closer to home.

A dedicated website (www.thecoldestjourney.org) will allow more than 42,000 schools across the UK access to the expeditions blog - and give them the chance to win an opportunity to talk to the team during the journey.

"This is the biggest ever interactive education website that the Department of Education has ever done. It will involve 42,000 state schools, a lot of other non-state schools and 200,000 across the Commonwealth."

Because the expedition is made up of people from the UK, Australia, New Zealand and South Africa, it will be completed under the Commonwealth flag.

"Rather than argue about which flag would be the expedition flag, it was decided to compromise and use a flag that covered all the people involved."

By the time the team complete their incredible journey, Sir Ranulph will be nearing 70. Is it time for him to put the snow boots away?

"Is this the last expedition? I have thought that for the last 20 years… It depends," he said. "It probably is the last big polar expedition but there are other things to do: mountains and deserts. I'm not sure."

Working for Sir Ranulph was "an honour"

The man who led the project for Sir Ranulph Fiennes said it was an honour to be part of the historic project.

Steve Mummery, operations manager at SF Engineering, said: "This project has definitely been a talking point. It makes a nice change from the run-of-the-mill work.

"It was quite an honour and a privilege to be involved. This expedition will go down in history."

He explained that Sir Ranulph called the St Ives firm personally to enquire about their services, having heard good things from the British Antarctic Survey, which is also an SF client.

Mr Mummery said: "When he rang, somebody here said to me 'I've got Ranulph Fiennes on the phone for you' It was a bit strange!

"When he explained what they were doing, I thought it was amazing."

He added: "It's a small part of our business. It's quite a limited market, working in the Antarctic!"

Mr Mummery said the expedition team at that point were still looking for volunteers to take part.

Asked if he considered it, Mr Mummery said emphatically: "No, definitely not!"