For our purposes, an offshore installation is an installation which is maintained, or intended to be established, for underwater exploitation or exploration. It does not include an installation which consists exclusively of a pipeline, whether or not part of it previously formed part of an offshore installation, nor does it include vessels, whether registered in the United Kingdom or elsewhere, which are dredging installations.

There are two basic types of installation, the mobile and the fixed. The mobile is one which can be moved from place to place without major dismantlement or modification, whether or not it has its own motive power, whilst the fixed is one which is not mobile. Insofar as they may be mentioned later, a concession owner is a person who has the right to exploit or explore the mineral resources in connection with which the installation is, or has been, or is to be used; while the owner is the person who has registered the installation, or if there is no such person, then the person who for the time being has management of it, or its main structure. The relevant waters or waters to which the Act of 1971 applies means largely the U.K. territorial waters and waters in areas designated by the Continental Shelf Act of 1964.

The Continental Shelf Act of 1964 represents the first real piece of legislation in respect of offshore exploration as we understand it today. It deals basically with providing powers to designate certain areas for exploration and exploitation, creating a 500-metre zone around installations operating in such areas in which the law of the U.K. is to operate and thus allowing for the creation of lots of little United Kingdoms beyond the seas, or at least the territorial seas. The only real safety aspect contained in that Act is the right of the Secretary of State to forbid the entry of ships into the 500-metre safety zone. Exceptions are made to this in respect of vessels entering by reason of repair to submarine cables in or near the zone; for the provision of services to the installation or the transporting of persons or goods to or from such, including inspectors authorised by the Secretary of State; ships belonging to the general lighthouse authority for the purposes of safety of navigation; ships attempting to save life or property, and ships forced to enter by stress of weather or when in distress.

This represented the main legislative activity in this sphere until June, 1971, when there was passed the Mineral Workings (Offshore Installations) Act, which finally