Where the property comprised in a long tenancy at a low rent is or includes residential premises, then at any time during the last two years of the term of the tenancy, or (if the tenancy is being continued after the term date by subsection (1) of section three of this Act) at any time while the tenancy is being so continued, the immediate landlord or any superior landlord may give to the tenant or any sub-tenant of premises comprised in the long tenancy a notice in the prescribed form requiring him to notify the landlord or superior landlord, as the case may be,—
and it shall be the duty of the person to whom such a notice is given to comply therewith within one month of the giving of the notice.
In this section the expression “residential premises” means premises normally used, or adapted for use, as one or more dwellings, the expression “sub-tenant” in relation to a long tenancy means the owner of a tenancy created (whether immediately or derivatively) out of the long tenancy and includes a person retaining possession of any premises by virtue of the Rent Act after the coming to an end of a sub-tenancy, and the expression “sub-tenancy” includes a right so to retain possession.