http://www.legislation.gov.uk/id/nisr/2015/70/schedule

SCHEDULEDEVELOPMENT PERMITTED UNDER ARTICLE 3

PART 30CROWN RAILWAYS, DOCKYARDS ETC. AND LIGHTHOUSES

Class A
Permitted development	A.	Development by or on behalf of the Crown on operational Crown land, required in connection with the movement of traffic by rail.
Development not permitted	A.1	Development is not permitted by Class A if it consists of or includes— a the construction of a railway; b the construction or erection of a hotel, railway station or bridge; c the construction or erection otherwise than wholly within a railway station of a residential building, an office, or a building used for manufacturing or repair work; or d the land is within a site of archaeological interest.
Interpretation of Class A	A.2	For the purposes of Class A references to the construction or erection of any building or structure includes references to the reconstruction or alteration of a building or structure where its design or external appearance would be materially affected.
Class B
Permitted development	B.	Development on operational Crown land by or on behalf of the Crown or its lessees, required— a for the purposes of shipping; or b in connection with the embarking. disembarking, loading, discharge or transport of military personnel, military equipment, munitions, and other items at a dock, pier, pontoon or harbour.
Development not permitted	B.1	Development is not permitted by Class B if— a it consists of or includes the construction or erection of a bridge or other building not required in connection with the handling of traffic; or b the land is within a site of archaeological interest.
Interpretation of Class B	B.2	For the purposes of Class B references to the construction or erection of any building or structure include references to the reconstruction or alteration of a building or structure where its design or external appearance would be materially affected.
Class C
Permitted development	C.	The use of any land by or on behalf of the Crown for the spreading of any dredged material resulting from a dock, pier, harbour, water transport, canal or inland navigation undertaking.
Class D
Permitted development	D.	Development by or on behalf of the Crown on operational Crown land, or for operational purposes, consisting of— a the use of land as a lighthouse, with all the requisite works, roads and appurtenances; b the extension of, alteration or removal of a lighthouse; or c the erection, placing, alteration or removal of a buoy or beacon.
Development not permitted	D.1	Development is not permitted by Class D if— a it consists of or includes the erection of offices, or the reconstruction or alteration of offices where their design or external appearance would be materially affected; or b the land is within a site of archaeological interest.
Interpretation of Class D	D.2	For the purposes of Class D— “buoys and beacons” include all other marks and signs of the sea; “lighthouse” includes any floating and other light exhibited for the guidance of ships, and also any sirens and any other description of fog signal.