Long-distance swimmer Lewis Pugh plans to kayak 1200km (745 miles) to the North Pole to raise awareness of how global warming has melted the ice sheet. The BBC's Jonah Fisher met him at his training camp in Cape Town, South Africa.
Lewis Pugh has spent his life swimming long distances. But after 20 minutes in the freezing water of the Arctic he decided that his future lay above the waves.
"It's been like trying to change from Roger Federer to Tiger Woods overnight," the 38-year-old British environmental campaigner told me at a training camp in South Africa.
Now, after months of tuition from Hungarian kayaking champion Robert Hegedus, Mr Pugh wants to become the first man to paddle to the North Pole.
"Nobody has ever attempted to kayak to the pole before. In fact, it would have been impossible last year because it was frozen over," he said.
Lewis Pugh did part of his training in the icy waters off northern Norway
This year, for the first time, scientists predict that the North Pole could briefly be ice free and that has inspired Mr Pugh to try to find a way through.
On Saturday he is due to set off on the 1200km (745 mile) expedition from Norway to the North Pole - a journey expected to take between two and three weeks. A support ship will follow the kayak to provide Mr Pugh with food and respite from the brutal conditions.
"This will be my hardest challenge to date," the self-proclaimed "Ice Bear" told me.
"It's a very long way across an ocean that is so cold, and with high winds. Recently when I was up there training I was wearing a wet suit and a dry suit and I was still freezing cold."
Until now, Lewis Pugh has been famous for completing long distance swims in all of the world's oceans. In 2006 the former lawyer swam the length of the River Thames and then in 2007 he swam 1km (0.6 miles) at the North Pole.
On both occasions Mr Pugh said he wanted to raise awareness of global warming and its affect on the polar regions.
A swimming purist, he has adhered strictly to the Channel Swimming Association rules, which has meant leaping into sub-zero water wearing just swimming trunks, cap and goggles.
Professor Tim Noakes runs the Institute of Sports Science in Cape Town, and has provided advice for all of Mr Pugh's Arctic adventures.
"The stress of the 20-minute swimming at the North Pole was extreme," Prof Noakes told me as Mr Pugh was put through a gruelling fitness test.
"But he knew it was 20 minutes and then it was over. The stress here is less for every session but he is going to have two or three weeks of paddling and that's going to be very, very demanding."
On the lush green slopes of Table Mountain, Lewis Pugh has been trying to prepare himself mentally.
Far away from the tourists queuing for the cable car he sits meditating and listening to music. For the first time in a lifetime of extreme challenges he is not sure that he wants to succeed.
"There's one side of me that desperately wants to get to the North Pole to be able to shake the lapels of world leaders to get them to understand what has happened there," he said.
"But then there's the other side of me that says I really hope I don't get there. I hope I fail because if I am able to get there we really are in deep trouble."
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