By Richard Black BBC environment correspondent

Almost a century of harsh weather has slowly taken its toll

The Nimrod hut at Cape Royds is one of the world's most at-risk monuments.

Shackleton's Nimrod expedition left the UK in 1907, and ended two years later after a perilous journey over the ice.

It came within 150km of the South Pole - the furthest south any group had been at the time - before turning back because of harsh weather.

Shackleton's party wintered in the Nimrod hut, which also provided shelter for ponies and a garage for the continent's first car.

Harsh weather

"It's a small hut, quite cosy, well-arranged," Bob Headland, Curator at the Scott Polar Research Institute in Cambridge, told BBC News.

I tend to say it is full of ghosts Bob Headland, Scott Polar Research Institute

"There is a large central stove, which was fed on anthracite; and a lot of things are still around - many supplies, and items you can read.

"I tend to say it is full of ghosts, though good friendly ones."

Robust the hut may have been, but almost a century of harsh weather has slowly taken its toll.

The World Monuments Fund describes it as one of the hundred most endangered sites in the world.

"With the fabric of it being eroded by ice particles - with the corrosion of materials - it's slow, but it's ineluctable," said Mr Headland.

"It's not very far from water which is salt and open for a large amount of the year - this memorial for the heroic age has a limited life which can be extended by quite an amount of work."

The work involves restoring some of the wooden planks used to build the hut, and repairing and replacing some of the artefacts inside - the cooking pots and food, the laboratory equipment, the skis and sledges.

"The huts themselves are still astonishingly similar to how they were when they were used," Martin Williams, the UK representative of the New Zealand Antarctic Heritage Trust, told BBC News.

"We don't want to create some Disneyland version - the idea is that people going in would experience something very similar to what they would have found if they had visited the hut just after the expedition."

Web based tour

It will be a long and expensive process, because workers can only stay there during the short Antarctic summer; the bill is expected to reach around $ 5 million.

Shackleton's Nimrod expedition left the UK in 1907, and ended two years later

Money has been pledged by individuals, by companies, and by the New Zealand government - though the UK government turned down an application for money from its National Heritage Memorial Fund.

Given its location, very few visitors will ever see the restored Nimrod hut in its full glory, though more may have the chance in the future for a web-based tour.

"Cruise ships usually go to the other side of the continent," said Mr Williams, "So the idea is to have some kind of virtual access; and we're talking to a number of organisations about how to do that."