How far can you ride a bike downhill? To find out GCN PresenterJames Lowsley-Williams has teamed up with adventurer Mark Beaumont for a challenge of epic proportions in the high Andes of Chile. Their goal is to scale the highest active volcano in the world, the Ojos del Salado, with bikes strapped to their backs, before riding the longest descent in the world….300 KM to the Pacific coast. With a depleted team, weather delays and pressure from home to return by Christmas, can they conquer the immense challenge ahead of them? It's all downhill from here... right?