(1) Except where rent is liable to periodical increase by virtue of an agreement entered into before the 1st day of January, 1939 or where rent is payable under a lease entered into before the 1st day of January, 1939, which has not expired before the first day of the period for which the rent is claimed, 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 null and void and shall be construed as if it were an agreement for the payment of the standard rent only.