Built during World War II in international waters off the English coast, the Maunsell forts were designed to protect the country from the German air forces. They were subsequently abandoned, until 1966, when Roy Bates, former officer in the Royal Navy, formed the project of seizing one of these forts in order to found a micronation there, which he then tried to have recognized by the international community.

In the framework of the “Principe Galápagos” and in the presence of members of government of the principality, Sealand Day (anniversary of the declaration of independence of the micronation in 1967) will be the culmination of the various activities and events linked to Sealand inside and outside of the Palais de Tokyo late August to early September.