In the fourth episode of the series Gethin Jones and Charlotte Uhlenbroek head to the North Pennines in search of adventure and to unearth adrenaline gold. Upper Teesdale is one of Britain’s least visited beauty spots but its geology makes for some truly spectacular waterfalls. On day one Charlotte sets off up river from High Force, England’s biggest waterfall to Cauldron Snout which lays claim to being England's longest waterfall.