Extreme sports magazine with Dougie Vipond. In the middle of winter, with 17 hours of darkness per day, nearly 500 competitors head north of Inverness for Britain's hardest mountain bike race - the Strathpuffer 24 hour marathon. Ice covers much of the course. This year, Dougie is partaking as a solo rider. Lindsay Cannon tries winter surfing. Cameron McNeish experiments with some very small bikes.