“(1) This Chapter does not apply to premises falling within section 72(1) if the internal floor area- (a) of any non residential part, or (b) (where there is more than one such part) of those parts (taken together), exceeds 25 per cent of the internal floor area of the premises taken as a whole). (2) A part of premises is a non-residential part if it is neither- (a) occupied, or intended to be occupied, for residential purposes, nor (b) comprised in any common parts of the premises…. (4) For the purpose of determining the internal floor area of a building or of any part of a building, the floor or floors of the building or part shall be taken to extend (without interruption) throughout the whole of the interior of the building or part, except that the area of any common parts of the building or part shall be disregarded.”
“I accept also Mr Gallagher’s contention that an unlawful use would have to be ignored for the purposes of applying para 1, and that the use of the living accommodation in the basement must be assumed to be in accordance with the user restriction in clause 2(13)….”