15.—(1) This paragraph applies where the landlord’s interest in the qualifying dwelling-house is leasehold.
(2) There is implied a covenant by the landlord to pay the rent reserved by the landlord’s lease and, except in so far as they fall to be discharged by the tenant, to discharge its obligations under the covenants contained in that lease.
(3) A covenant implied by virtue of paragraph 14 (implied covenants where qualifying dwelling-house is a flat) shall not impose on the landlord an obligation which the landlord is not entitled to discharge under the provisions of the landlord’s lease or a superior lease.
(4) Where the landlord’s lease or a superior lease, or an agreement collateral to the landlord’s lease or a superior lease, contains a covenant by a person imposing obligations which, but for sub-paragraph (3), would be imposed by a covenant implied by virtue of paragraph 14, there is implied a covenant by the landlord to use its best endeavours to secure that that person’s obligations under the first-mentioned covenant are discharged.