Father Christmas wouldn't look out of place in the winter wonderland that provides the backdrop for one of television's most breathtaking productions.

But appearances can be deceptive.

There's nothing remotely cosy about the majestic landscape in Channel 4's epic 'Shackleton', which is the most ambitious and expensive drama ever made by the channel with a £10 million price tag. Think Scott of the Antarctic with a happy ending and plenty of heroic stuff in between.

Kenneth Branagh stars as the explorer Sir Ernest Shackleton who led a team that aimed to be the first to reach the South Pole by land.

Shackleton's crew of 27 men and a cat called Mrs Chippy boarded their ship Endurance in 1914 and headed south into an amazing adventure that could have killed them all.

The ship was trapped and eventually crushed in ice, leaving the crew stranded in one of the most inhospitable climates known to man. But amazlingly, after a two-year trek across the ice and snow, Shackleton managed to lead his men to safety.

Shackleton is a story of amazing bravery and physical courage - the men rowed hundreds of miles across stomry waters and pulled lifeboats and supplies over glaciers.

No wonder the programme is so spectacular. It took six months to make, with sets built at Shepperton Studios including a replica of the decks of the Endurance that had to tilt and flood with water to re-create the sinking.

But the most demanding element of the filming process was the five weeks which were spent on location in the sea-ice off Eastern Greenland, re-creating the crew's spectacular and dangerous journey. The cats and crew stayed on a Norwegian ice-breaking ship called the Polar Bird, which kept them warm and dry. But filming outside on ice floes, which could break and float off at any time, was cold, wet and extremely dangerous.

"We were beautifully fed and very well looked after, but the cold weather made you peculiarly hungry and potentially cranky," Branagh remembers. "Someone who arrived on the set brought a bag full of Mars Bars with them and started asking if anyone would like one.

"People were scattered all over the set, but when they realised there was the prospect of chocolate it was like a pack of rats desacending on this poor woman, who was practically savaged by people obsessed by the thought of chocolate at 4 pm on a freezing afternoon.

"Some people got a bit narked if they didn't get any, or if someone had eaten one without offering to share it. The Mars Bar Incident certainly produced a bit of drama. The diaries of the crew on Shackleton's expedition contain snippets of their obsession without finding food, so I think we got a sense of what that must have been like."

Even though the crew was obviously safer than the members of Shackleton expedition, filming on constantly moving ice in Greenland was still a very risky operation, and conditions could change within seconds.

"There was a bit where myself, Kevin McNally and Lorcan Cranitch were supposed to do a shot, and we had a conversation with writer and director Charles Sturridge about whether to do the shot then or after lunch.

"We decided to wait until afterwards, which was a good job, because while we were having lunch, a huge crack in the ice opened up exactly where we would have been standing, and if we'd been there, we'd have been drifting towards the coast of Greenland. It certainly kept us on our toes.

"The entire cast was in three small boats, with the saftey crew in another following behind. We had one radio to keep in contact - which we dropped in the water. We thought, 'This is so dangerous - if anything happened, we could lose half the actors' union Equity here!'

"There was certainly a frisson of danger about filming there - ice floes off Greenland aren't the sort of place you'd go on holiday - but it was a privilege to be in that environent. And it really brought out the best in people."