The Town and Country Planning (General Permitted Development) Order 1995

A.2    Conditions

Development is permitted by Class A subject to the following conditions—

(a)any system apparatus shall, so far as practicable, be sited so as to minimise its effect on the external appearance of any building or other structure on which it is installed;

(b)any system apparatus which is no longer needed for a driver information system shall be removed as soon as reasonably practicable.