17In any case where, prior to the date of termination of a long residential tenancy, the landlord and the tenant agree for the grant to the tenant of a future tenancy of the whole or part of the property let under the tenancy at a rent other than a low rent and on terms and from a date specified in the agreement, the tenancy shall continue until that date but no longer; and, in such a case, the provisions of this Schedule shall cease to apply in relation to the tenancy with effect from the date of the agreement.