The Maunsell Forts are towers built in the Thames and Mersey estuaries during the Second World War to help defend the United Kingdom.

[4] The twin concrete supporting towers were divided into seven floors, four for crew quarters;[4] the remainder provided dining, operational, and storage areas for several generators, and for fresh water tanks and antiaircraft munitions.

The design of these concrete structures is equal to a military grade bunker, due to the ends of the stilts (under water), that are locked into the ground.

[5] Rough Sands fort was built to protect the ports of Felixstowe, Harwich and the town of Ipswich from aerial and sea attack.

He and his son were arrested and charged, but the court dismissed the case as it did not have jurisdiction over international affairs: Roughs Tower lay beyond the territorial waters of Britain.

Bates took this as de facto recognition of his country and seven years later issued a constitution, flag, and national anthem, among other things, for the Principality of Sealand (founded on 2 September 1967).

On 18 August 1967 Sunk Head was boarded by a contingent of the 24th Field Squadron of Royal Engineers from Maidstone from the tug Collie, commanded by Major David Ives.

[10] Tongue Sands Fort was situated approximately 10.2 kilometres (6 nmi) from the coast off Margate, Kent and was grounded on 27 June 1942.

[12] During the mid-1960s under-scouring had further distorted the fort: large holes had appeared in east leg, sea water had flooded the lower levels and the platform had become detached with huge gaps between the deck.

Tongue Sands Fort finally collapsed into the under-scouring hole during storms on 21/22 February 1996, leaving only a single 18 foot stump of the south leg remaining visible above sea level.

[11] During World War II, the Thames estuary forts shot down 22 aircraft and about 30 flying bombs; they were decommissioned by the Ministry of Defence during the late 1950s.

[citation needed] Other forts were in international waters until the three-mile limit was extended to 12 nmi (14 mi; 22 km).

During that time, the fort was also used as the setting for the third season finale episode, "Not So Jolly Roger" (first aired on 7 April 1966), of the 1960's UK television series Danger Man (known as Secret Agent in the U.S.) starring Patrick McGoohan; that episode concerned a pirate radio station that was a front for spies passing on secrets, and included substantial scenes filmed on location at the fort.

During the early 21st century, in response to proposals to demolish the fort, a group named Project Redsands was formed to try to preserve it.

[23] This group was built near the Thames estuary for anti-aircraft defence and made up of several towers north of Herne Bay 9.2 mi (8.0 nmi; 14.8 km) from the nearest land.

Demolition of the structures started during the 1950s with these forts considered a priority over the Thames estuary ports due to being a hazard to shipping.

In order to prevent further illicit broadcasting, a team of Royal Engineers laid 2,200 lbs of explosive charges on Sunk Head, commencing on 18 August 1967.

[29] Paddy Roy Bates occupied the Knock John Fort in 1965 and established Radio Essex, later renamed BBMS—Britain's Better Music Station, but was better known for his post-pirate activities.

[30] The 1966 television series Danger Man episode "Not-so-Jolly Roger" was filmed partly at Redsands Army Sea Fort and includes an acknowledgement to Radio 390 in its closing credits.

Redsands Fort was also used for the 1968 Doctor Who serial Fury from the Deep, in which the complex stood in for a North Sea gas refinery besieged by an intelligent seaweed creature.

In the 2013 movie The Hunger Games: Catching Fire, as the characters travel in a train along the coast, two Sea Forts can be seen in the water.

The setting of the 2023 science fiction film Last Sentinel is based on a structure modelled after a single tower of the Maunsell army forts.

[33] [34] The Red Sands Forts are seen in Episode 1 of Whitstable Pearl, mentioned as a drop-off and pick-up point for illicit drugs, as part of the story.