One hundred years ago, Sir Ernest Shackleton tried, but narrowly failed, to become the first man to reach the South Pole. Descendants of his team have been retracing and completing his journey.
Descendants of polar explorer Ernest Shackleton and his expedition visit the hut he built 100 years ago where his team spent an Antarctic winter
A glorious day for our start. Brilliant sunshine and a cloudless sky. Fair wind from the north. Breakfast at 7am. We started to strive to plant the King's flag on the last spot in the world
Ernest Shackleton, 1908 (centre)
There was no map of the Antarctic in 1908 when the men of Shackleton's expedition set out for the South Pole.
The unexplored continent was marked as "terra incognita" or land unknown and Shackleton's only guide as they set out was a compass.
"A glorious day for our start. Brilliant sunshine and a cloudless sky. Fair wind from the north. Breakfast at 7am. We started to strive to plant the King's flag on the last spot in the world"
A century later, the three men, setting out on the route pioneered by Shackleton must trek the equivalent of 35 marathons in 70 days.
And they must complete the 800 nautical miles (equivalent to 920 miles or 1420km) across some of the most extreme terrain and conditions on the planet.
LEFT: Henry Adams, great grandson of Shackleton's second in command, Jemson Adams
CENTRE: Lt Col Henry Worsley, relative of Shackleton's ship's captain Frank Worsley
RIGHT: Will Gow, Shackleton's great nephew
All their fuel, food and equipment is carried in sleds behind them. And for inspiration, they have a copy of Shackleton's diary.
"We read The Heart of the Antarctic every night and pick out bits of his diary that are absolutely spot on to where we have got to on the journey ," says the team leader, Henry Worsley who is a lifelong admirer of Shackleton.
The first challenge of the journey is to cross 350 miles of the Ross Ice Shelf, a flat expanse covered in powder snow. Progress is good until high winds leave the three men stuck in their tent for two days.
Shackleton, they read, endured the same and worse. "Blowing a blizzard, with thick drift from south by west. It is very hard to be held up like this. We only had a couple of biscuits each for lunch for I can see we must retrench at every setback if we are to have enough food to carry us through."
The biggest obstacle on the route are the TransAntarctic Mountains. Remarkably, Shackleton managed to find a route across up the Beardmore Glacier, "a great highway unfolding from north to south." as he describes it.
The other great challenge of the Beardmore is the surface itself - mile upon mile of iron-hard blue ice that has been stripped of snow, then scoured and polished by the wind
More than 120 miles long, 25 miles wide and rising over 7000 feet to the Antarctic plateau it is one of the largest glaciers in the world and is riddled with deadly crevasses - the cracks that form in the ice as a glacier buckles and twists.
Like Shackleton before them, the crevasses were a constant danger for the 2008 expedition. The team members had to travel roped together in case of a fall.
The other great challenge of the Beardmore is the surface itself - mile upon mile of iron-hard blue ice that has been stripped of snow, then scoured and polished by the wind.
"Its a frozen hell. If hell was cold this would be it," says the expedition leader, Henry Worsley. "It's so enormous, it's beyond intimidating."
The modern team are equipped with metal spikes strapped to the bottom of their boots to give them a grip on the bare ice.
Shackleton describes days of "cuts, bruises....and iron hard ice" and "desperate pulling today" as he was forced to cut the rations because of the slow progress.
The Antarctic plateau is the most inhospitable place on earth.
But by Christmas, both teams had finally made it up the Beardmore and were on the Antarctic plateau which stretches all the way to the pole.
But far from a relief, the high ground proved to be even tougher than climbing the glacier. It is the coldest, driest place on earth with an average altitude of almost two miles.
As well as extreme cold and high wind, there are the symptoms of altitude sickness - headaches, nausea and a loss of appetite.
The team found it hard to eat, but it's vital to keep taking in calories, as Henry Adams explained. "Every single break time you sit there for five or ten minutes...you've got to eat your food....you become a combination of an animal and a machine."
A century earlier Shackleton too was shocked by the brutality of conditions on the plateau, and by January 2nd 1909 there were intimations in his diary that the Pole might be beyond their grasp.
"Terribly hard work today. We are weakening from want of food and the high altitude. I cannot think of failure yet. I must look at the matter sensibly and consider the lives of those who are with me. Man can only do his best and we have arrayed against us the strongest forces of nature."
Finally, on the 9th of January 1909 Shackleton reached his furthest south - just 97 nautical miles from the pole. He realised that if they carried on to the pole his team would not have enough food to return.
To save the lives of his men he made the decision to turn back.
With all the benefits of modern equipment, the 2008-9 team were able to complete Shackleton's journey but their admiration for Shackleton, who brought all his men home safely, remains.
"The decision to turn back must be one of the greatest decisions taken in polar exploration," says Worsley.
"It is a great tribute to the man in terms of his love of his men. No-one was going to die and no-one was going to be seriously injured on his command."
Timewatch: In the footsteps of Shackleton is on Saturday 4 April at 2040BST on BBC Two. Also available for seven days atBBC iPlayer
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