Nick Crane pays tribute to the unsung mega-port of Immingham. It's a city-sized enterprise dedicated to global trade and the biggest seaport in the UK, in terms of the weight of goods it handles. He discovers how this east coast energy importer has been specially engineered to import the coal needed to generate electricity. Can he master the controls of a crane? He also meets the foreign crew of a super-tanker who spend months of their lives at sea.

Tessa Dunlop uncovers the story of how Hitler's bombers could have drowned London, and possibly won the Second World War, by destroying the embankments that contain the River Thames. Tessa reveals the secret wartime defensive schemes, devised to prevent the Thames flooding the capital city during air raids. To protect those sheltering in the tube network, a chain of underwater microphones and steel floodgates was installed, with the evidence still visible today.

Ruth Goodman investigates the clandestine coastal sex trade that scandalised Victorian Britain. In the mid-19th century the Royal Navy was in crisis as sailors fell prey to sexually transmitted diseases. The government brought in laws to detain and forcibly treat women suspected of being prostitutes, but social campaigner, Josephine Butler, was determined to take on the establishment.

Mark Horton reveals how solving the greatest scientific puzzle of the 18th century, determining a ship's exact position at sea, meant Greenwich became the epicentre of global sea navigation. The problem of working out a vessel's longitude had foiled the world's best brains, so the British government offered a prize to any member of the public who could crack longitude.

In Liverpool, world champion free runner Ryan Doyle shows off his skills around the city's docklands. Show less