Britain's coastline is defined by the wind, rain, sun and tides, and these forces of nature influence the lives of every single living thing here. Alan Titchmarsh braves the elements to find out why our coastline is such an extraordinary place for wildlife, from the giant minke whale to the tiny snail bee, the elegant arctic tern to the plodding toad, and the fastest seabird in the west to one of the world's greatest predators.