Just how far can you ride a bike In 24 hours? Ultra-endurance cyclist Mark Beaumont is joined by GCN Presenter James Lowsley-Williams on an overnight expedition from Somerset to Scotland through gruelling winter conditions. Along the way they are tested by a team of top academics to monitor the effect of the demanding challenge is having on their cognitive function and long term physical ability. Battling fatigue and the ever-changing weather conditions, how far can they make it?