In this special edition of Countryfile, Ellie Harrison tells the story of one of our greatest rivers - the Humber. She explains how it has shaped the landscape, nourished all kinds of wildlife and been an aide to human endeavour. She follows its course from one of its key tributaries to where it flows out beyond the world famous Humber Bridge to the North Sea. It is a tale of the Derwent, the Ouse and ends with an epic voyage down the Humber itself onboard a sloop - a traditional working boat. Along the way, Ellie will be looking back at some of Countryfile's finest moments out on the water. Matt Baker joins the RNLI flood rescue team in a training exercise on the river Etive. Julia Bradbury finds out how rivers have shaped our industries when she visits woollen mills in west Yorkshire. And in Wales, Jules Hudson goes on a hike with a difference while Matt takes on the might of the Severn Bore.