If a request under section 21 (request for summary of relevant costs) relates in whole or in part to relevant costs incurred by or on behalf of a superior landlord, and the landlord to whom the request is made is not in possession of the relevant information—
he shall in turn make a written request for the relevant information to the person who is his landlord (and so on, if that person is not himself the superior landlord),
the superior landlord shall comply with that request within a reasonable time, and
the immediate landlord shall then comply with the tenant's or secretary's request, or that part of it which relates to the relevant costs incurred by or on behalf of the superior landlord, within the time allowed by section 21 or such further time, if any, as is reasonable in the circumstances.
If a request under section 22 (request for facilities to inspect supporting accounts, &c.) relates to a summary of costs incurred by or on behalf of a superior landlord—
the landlord to whom the request is made shall forthwith inform the tenant or secretary of that fact and of the name and address of the superior landlord, and
section 22 shall then apply to the superior landlord as it applies to the immediate landlord.