Ever since ancient Rome, the sea, seabed and seashore have been accepted as part of the commons—res communes omnium—belonging to everybody equally, and inalienable as state or private property. The commons as a distinct form of property was taken forward in Magna Carta and the Charter of the Forest of 1217, the twin bedrocks of common law and all democracies.
A commons depends on the “sovereign”—in the UK’s case, the monarchy—acting as steward or trustee, with responsibility for preserving it for generations to come. For more than 650 years, following a ruling by King Edward I in 1299, the monarchy accepted this positive duty, known as the Public Trust Doctrine.