From the Isle of Man, Michael Portillo crosses the Irish Sea, bound for the mighty port of Liverpool and its historic waterfront.At the International Slavery Museum in Royal Albert Dock, he reflects on the city's part in the transatlantic trade in enslaved people. He takes Merseyrail to Birkenhead, where he inspects a German U-boat before seeing the underground room where the Battle of the Atlantic was monitored and controlled.In Crosby, he encounters dozens of west-facing iron men before heading off to Blackpool, where he learns about the city's wartime experiences.