(1)  Where a landlord has at any time, before the commencement of this Act with or without the approval of the tenant or after the commencement of this Act with the written approval of the tenant or of the Controller, incurred expenditure for any improvement, addition or structural alteration in the premises, not being expenditure on decoration or tenantable repairs necessary or usual for such premises, and the cost of that improvement, addition or alteration has not been taken into account in determining the rent of the premises, the landlord may lawfully increase the standard rent per year by an amount not exceeding ¹[ten per cent.] of such cost.

   (2)  Where a landlord pays in respect of the premises any charge for electricity or water consumed in the premises or any other charge levied by a local authority having jurisdiction in the area which is ordinarily payable by the tenant, he may recover from the tenant the amount so paid by him; but the landlord shall not recover from the tenant whether by means of an increase in rent or otherwise the amount of any tax on building or land imposed in respect of the premises occupied by the tenant:

   Provided that nothing in this sub-section shall affect the liability of any tenant under an agreement entered into before the 1st day of January, 1952, whether express or implied, to pay from time to time the amount of any such tax as aforesaid.