(a) the contract must be in writing and registered, (Z>) the rent must not be enhanced so as to exceed by more than three annas in the rupee the rent previously payable by the tenant, and
(r) the rent fixed by the contract shall not be liable to enhancement during a term of six years from the date of contract:
Provided as follows :—
(i) Nothing in clause (a) shall prevent a landlord from recovering rent at a rate at which it has been actually paid for a conti nuous period of not less than three years immediately preceding the period for which the rent is claimed.
(it) Nothing in clause (/>) shall apply to a contract by which a tenant binds himself to pay an enhanced rent in consideration of an improvement which has been or is to be effected in respect of the holding by or at the expense of his landlord and to the benefit of which the tenant is not otherwise entitled ; but an enhancement fixed by such a contract shall be payable only when improvement has been effected ; provided that such enhancement shall also be payable if the tenant is responsible for any default in respect of the im provement.