In the middle of winter, with 17 hours of darkness, over 500 competitors head north of Inverness for one of the world's toughest mountain bike races - the Strathpuffer 24. It's the largest ever 'Puffer - an event where competitors push themselves and their bikes to the very limit. And making the most of the night time we join the man they call the 'moonwalker' because he thinks the best time to explore our hills is in the dark. In contrast Cameron McNeish sings their praises during the short daylight winter hours. And we're off to one of the coldest and most extreme places in the world, where some intrepid Scots are blazing a trail.