4.—(1) If the Secretary of State or the local planning authority is satisfied that it is expedient that development described in any Part, Class or paragraph in Schedule 2, other than Class K or M of Part 17, should not be carried out unless permission is granted for it on an application, the Secretary of State or (as the case may be) the local planning authority, may make a direction under this paragraph that the permission granted by article 3 does not apply to—
(a)all or any development of the Part, Class or paragraph in question in an area specified in the direction; or
(b)any particular development, falling within that Part, Class or paragraph, which is specified in the direction,
and the direction must specify that it is made under this paragraph.
(2) A direction under paragraph (1) does not affect the carrying out of—
(a)development permitted by any Class in Schedule 2 which is expressed to be subject to prior approval where, in relation to that development, the prior approval date occurs before the date on which the direction comes into force and the development is completed within a period of 3 years starting with the prior approval date;
(b)development permitted by Class B of Part 9 of Schedule 2;
(c)development mentioned in Class A of Part 16 of Schedule 2, unless the direction specifically so provides;
(d)development permitted by Class A of Part 18 of Schedule 2 authorised by an Act passed after 1st July 1948 or by an order requiring the approval of both Houses of Parliament approved after that date;
(e)development permitted by Class Q, R, S or T of Part 19 of Schedule 2;
(f)development permitted under Schedule 2 in an emergency.
(3) A direction made or having effect as if made under this article does not, unless the direction so provides, affect the carrying out by a statutory undertaker of the following descriptions of development—
(a)the maintenance of bridges, buildings and railway stations;
(b)the alteration and maintenance of railway track, and the provision and maintenance of track equipment, including signal boxes, signalling apparatus and other appliances and works required in connection with the movement of traffic by rail;
(c)the maintenance of docks, harbours, quays, wharves, canals and towing paths;
(d)the provision and maintenance of mechanical apparatus or appliances (including signalling equipment) required for the purposes of shipping or in connection with the embarking, disembarking, loading, discharging or transport of passengers, livestock or goods at a dock, quay, harbour, bank, wharf or basin;
(e)any development required in connection with the improvement, maintenance or repair of watercourses or drainage works;
(f)the maintenance of buildings, runways, taxiways or aprons at an aerodrome; or
(g)the provision, alteration and maintenance of equipment, apparatus and works at an aerodrome, required in connection with the movement of traffic by air (other than buildings, the construction, erection, reconstruction or alteration of which is permitted by Class F of Part 8 of Schedule 2).
(4) The procedures which must be followed in making, modifying or cancelling any direction made under article 4(1) are set out in Schedule 3.
(5) In this article and in Schedule 3—
“local planning authority” means the local planning authority whose function it would be to determine an application for planning permission for the development to which the direction relates or is proposed to relate; and
“prior approval date” means the date on which—
prior approval is given;
a determination that such approval is not required is given, or
any period for giving such a determination has expired without the applicant being notified whether prior approval is required, given or refused.