Where under Part I of this Act the competent landlord is required by an agreement, or by a determination of the court, to carry out initial repairs to any premises, he may serve on any mesne landlord a notice requiring him to pay to the competent landlord a contribution towards the cost reasonably incurred by the competent landlord in carrying out those repairs, if and in so far as that cost is not recovered by way of payment for accrued tenant’s repairs and is not recoverable (apart from this sub-paragraph) otherwise than by way of such payment.

Where a notice has been served under the last foregoing sub-paragraph, then in default of agreement between the competent landlord and the mesne landlord on whom the notice was served the court may order the mesne landlord to pay such a contribution as aforesaid.

A contribution ordered under this paragraph shall be such as the court determines to be reasonable having regard to the difference between the rent under the relevant tenancy and the rent which, if the tenant retains possession, will be recoverable . . . F1, during the period of the statutory tenancy.