4. An agreement between the competent landlord and the tenant made for the purposes of this Order in a case where—N.I.
(a)the competent landlord is himself a tenant; and
(b)the agreement would apart from this paragraph operate as respects any period after the coming to an end of the estate of the competent landlord,
shall not have effect unless every superior landlord who will be the immediate landlord of the tenant during any part of that period is a party to the agreement.