Sch THIRD Pt III para 1
If the tribunal by whom the compensation is to be assessed are satisfied with respect to any premises that the rental thereof was enhanced by reason of their being used for illegal purposes, or being overcrowded within the meaning of Part IV of this Act, the compensation shall, so far as it is based on rental, be based on the rental which would have been obtainable if the premises were occupied for legal purposes, and were not so overcrowded.