(1)  Except where rent is liable to periodical increase by virtue of an agreement entered into before the 1st day of January, 1939, no tenant shall, notwithstanding any agreement to the contrary, be liable to pay to his landlord for the occupation of any premises any amount in excess of the standard rent of the premises, unless such amount is a lawful increase of the standard rent in accordance with the provisions of this Act.

   (2)  Subject to the provisions of sub-section (1) any agreement for the payment of rent in excess of the standard rent shall be construed as if it were an agreement for the payment of the standard rent only.