Imagine going on a bike ride that lasts for 4 years. Now he wants to try something really hard.
Alastair cycled around the world for 4 years, raced a yacht across the Atlantic Ocean and he is currently training for The Bob Graham Round and preparing for SOUTH, the first unsupported return journey to the South Pole and the longest unsupported polar journey in history. 
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Recorded live at the global event in Cardigan, west Wales in 2009.
Watch Alastair's full talk here: www.thedolectures.com/talks/alastair-humphreys-the-importance-of-jumping-in-rivers