An existing landlord and tenant shall, as soon as possible but not later than two years from the date of coming into force of this Act, bring the tenancy in conformity with the provisions of this Act. An agreement to sell or any other agreement entered into between the landlord and the tenant, after the execution of a tenancy agreement, in respect of premises and for a matter other than a matter provided under the tenancy agreement, shall not affect the relationship of landlord and tenant unless the tenancy is revoked through a written agreement entered before the Rent Registrar in accordance with the provisions of section.