The Maunsell Forts are armed towers built in the Thames and Mersey estuaries during the Second World War to help defend the United Kingdom.
They were operated as army and navy forts, and named after their designer, Guy Maunsell. The forts were decommissioned in the late 1950s and later used for other activities including pirate radio broadcasting. In the summers of 2007 and 2008 Red Sands Radio, a station commemorating the pirate radio stations of the 1960s, operated from the Red Sands fort. The fort was subsequently declared unsafe, and Red Sands Radio has moved its operations ashore to Whitstable.