Rusted concrete towers on spindly stilts rise straight out of the sea off the English coast, looking like an abandoned dystopian film set. These are the Maunsell Forts, and their history swings wildly from absolute state control to outright rebellion against it.

This episode traces the forts from top-secret World War II air defenses, prefabricated on land and sunk into the seabed, to their afterlife as outlaw pirate radio stations and even a self-declared micronation. We explore the engineering, the wartime combat, the slow surrender to the sea, and the strange cultural legacy of structures built to impose order that became havens for escaping it.

• How 4,500-ton forts were built in dry docks, floated out, and sunk onto sandbanks
• The night Tongue Sands fort so confused German E-boats that one rammed another
• The pira ...