The series continues with a journey from Cornwall to South Wales. Neil Oliver casts his own bronze sword and discovers how demand for tin 3,500 years ago put Cornwall at the centre of an international arms trade. Neil also explores the site of the 'Welsh Great Escape' when nearly 70 German prisoners of war were on the loose in the sand dunes after tunnelling out of a prisoner of war camp on the coast of Wales. Newcomer to Coast and champion surfer Renee Godfrey swims with seals and searches out rare corals on the island paradise of Lundy. On Exmoor's treacherous sea cliffs, Nick Crane is challenged to an epic sideways climb, originally inspired by the conquest of Everest. Nick meets the men who set a record for this uniquely British endurance test. Hermione Cockburn discovers how American media mogul William Randolph Hearst, the inspiration for Citizen Cane, transformed a run-down castle on the Welsh coast into a fabulous fun palace for the rich and famous. The last family of 'mud-horse' fishermen reveal the fruits of a day's work on the Severn Estuary mudflats, and Mark Horton visits Bristol to uncover the story of Samuel Plimsoll. He became a national hero in the 1800s when he campaigned against the corruption of ship-owning MPs, and made sailors safer by painting a simple line on the side of ships.