During the Second World War, the British government built several Fortress islands in the North Sea to defend its coasts from German invaders. Some of these forts were built illegally in international waters.

One of these illegal Fortresses, consisting of concrete and steel construction, was the famous Fort Roughs Tower, situated slightly north of the estuary region of the River Thames, on the east coast of the United Kingdom. In contrast to the original plan to locate the tower within the sovereign territory of the UK, this fortress was situated at a distance of approximately 7 nautical miles from the coast. This is more than double the then applicable 3 mile range of territorial waters. To put it briefly, this island was situated in the international waters of the North Sea.

The forts were abandoned in the early 1950’s and, due to their illegal construction in international waters in a time of world crisis, they should have been destroyed, to comply with international law. Except for the aforementioned fortress, similarly located fortresses were subsequently pulled down. The result of this was the portentous uniqueness of the fortress. Fort Roughs Tower, situated on the high seas, had been deserted and abandoned, res derelicta and terra nullius. From a legal point of view, it therefore constituted extra-national territory.