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Colin Stafford-Johnson and Lucy Cooke begin a week-long adventure around the UK's wilderness, beginning with a look at the country's rivers. Colin travels up the River Wye following the salmon, while Lucy discovers the wilder side of canals at night . We go behind the scenes with Steve Backshall and the Wild Alaska Live team as they try to film the elusive salmon shark There is also a look at how the return of one of Britain's long-lost beasts, the beaver, is changing the landscape, as well as how the UK's rivers are important for one of the world's most peculiar fish - the sea lamprey.