(1)Subject to the provisions of this section, in these provisions " office premises" means premises falling within either of the following descriptions, that is to say—
(a)premises whose sole or principal use is to be use as an office or for office purposes;
(b)premises to be occupied together with premises falling within the preceding paragraph and to be so occupied wholly or mainly for the purposes of the activities to be carried on in the last-mentioned premises.
(2)Where, in relation to an application for planning permission for the erection of a building, or in relation to a grant of such planning permission, it falls to be determined, for the purposes of subsection (1) of this section, what is to be the sole or principal use of any premises to be contained in the building, regard shall be had—
(a)in the case of an application for planning permission, to the proposed use (as indicated in the application) of the building or of different parts of the building; and
(b)in the case of a grant of planning permission, to the purposes specified in the planning permission as those for which the building, or different parts of the building, may be used.
(3)Where, in relation to an application for planning permission for the extension or alteration of a building, or in relation to a grant of such planning permission, it falls to be determined, for the purposes of subsection (1) of this section, what is to be the sole or principal use of any premises which are to be added to the building or altered within it (in this subsection referred to as " the new premises " ), regard shall be had—
(a)in the case of an application for planning permission, to the proposed use (as indicated in the application) of the new premises; and
(b)in the case of a grant of planning permission, to the purposes specified in the planning permission as those for which the new premises may be used.
(4)For the purposes of the application of these provisions in relation to development in so far as it consists of a change in the use of land " office premises " (subject to the following provisions of this section) means premises falling within either of the following descriptions, that is to say—
(a)premises whose sole or principal use is as an office or for office purposes;
(b)premises occupied together with premises falling within the preceding paragraph and so occupied wholly or mainly for the purposes of the activities carried on in the last-mentioned premises;
and for the purposes of paragraph (a) of this subsection any question as to sole or principal use, in relation to premises contained in a building, shall be determined by reference to those premises alone and not by reference to the building taken as a whole.
(5)In this section " office purposes " includes the purposes of administration, clerical work, handling money, telephone and telegraph operating and the operation of computers, and " clerical work" includes writing, book-keeping, sorting papers, filing, typing, duplicating, punching cards or tapes, machine calculating, drawing and the editorial preparation of matter for publication.
(6)The Secretary of State may by order provide that premises of any description specified in the order, or premises used or to be used for any purposes so specified, shall not be office premises for the purposes of these provisions.
(7)In this section, in sections 74 to 86 of this Act and in Schedule 12 to this Act " these provisions " means the provisions of this section, of those sections, of that Schedule and of Schedule 13 to this Act.