68.—(1) A covenant in a lease (whether made before or after the commencement of this Act) of a tenement absolutely prohibiting the making of any improvement within the meaning of section 67 (3) on the tenement shall have effect as if it were a covenant prohibiting the making of the improvement without the licence or consent of the lessor.

(2) In every lease (whether made before or after the commencement of this Act) of a tenement in which there is contained a covenant prohibiting either expressly or by virtue of subsection (1), the making of any improvement within the meaning of section 67 (3) on the tenement without the licence or consent of the lessor, the covenant shall, notwithstanding any express provision to the contrary, be subject—

(a) to a proviso that the licence or consent shall not be unreasonably withheld, and

(b) to a proviso that no fine or sum of money in the nature of a fine (other than a reasonable sum in respect of legal or other expenses incurred by him in connection with the licence or consent) nor any increase of rent shall be payable for or in respect of the licence or consent.