Proof of consent etc. of Board or Housing Commissioner or Chairman

Whenever, under this Act or any rule or regulation or byelaw made there-under, the doing or the omission to do anything or the validity of any thing depends upon the approval, sanction, consent, concurrence, declaration, opinion, or satisfaction of - (a) The Board or Chairman or Housing Commissioner; (b) Any officer or servant of the Board; a written document signed in case (a) by the Chairman and in case (b) by the said officer or servant, conveying, or setting forth such approval, sanction, consent, concurrence, declaration, opinion or satisfaction shall be sufficient evidence of such approval, sanction, consent, concurrence, declaration, opinion or satisfaction.