Proportion of improvement expenses may be deducted from rent.

(1) Where the occupier by whom any improvement expenses are paid holds the premises on which the expenses together with interest thereon are charged, at a rent not less than the rack-rent, he shall be entitled to deduct three-forths of the amount paid by him on account of such expenses and interest thereon as aforesaid from the rent payable by him to his landlord, and, if he holds at a rent less than the rack-rent, he shall be entitled to deduct from the rent so payable by him such proportion of three-forths of the amount paid by him on account of such expenses and interest thereon as aforesaid as his rent bears to the rack-rent. (2) If the landlord from whose rent any deduction is so made is himself liable to the payment of rent for the premises in respect of which the deduction is made and holds the same for a term of which less then twenty years is unexpired (but not otherwise), he may deduct from the rent so payable by him such proportion of the sum deducted from the rent payable to him as the rent payable by him bears to the rent payable to him, and so in succession with respect to every landlord (holding for a term of which less then twenty years is unexpired) of the same premises both receiving and liable to pay rent in respect thereof : Provided that nothing in this section shall be construed to entitle any person to deduct from the rent payable by him more then the whole sum deducted from the rent payable to him.