48.—(1) Where a tenant proposes to make an improvement to his tenement, he may serve on his landlord a notice in the prescribed form (in this Act referred to as an improvement notice) together with—

(a) in every case—

(i) a statement of the works proposed for making the improvement, and

(ii) an estimate, verified by an architect, surveyor or building contractor, of the cost of making the improvement, and

(b) if the improvement is development for which planning permission is required, a copy of the permission.

(2) Where an improvement notice is served, the landlord may, within one month, serve on the tenant any one of the following notices:

(a) a notice (in this Act referred to as an improvement consent) in the prescribed form consenting to the making of the improvement,

(b) a notice (in this Act referred to as an improvement undertaking) in the prescribed form undertaking to execute the improvement in consideration of either (as the landlord states in the notice) a specified increase of rent or an increase of rent to be fixed by the Court,

(c) subject to subsection (3), a notice (in this Act referred to as an improvement objection) in the prescribed form objecting to the improvement on grounds specified in the notice.

(3) An improvement objection may be served only where the grounds of the objection are—

(a) that the tenant holds the tenement otherwise than under a lease for a term of which at lease five years are unexpired at the time when the improvement notice is served, and

(b) that the tenant would, on any of the grounds specified in section 17 (2) (a), not be entitled under Part II to a new tenancy.

(4) Where an improvement notice is served in a case in which the landlord holds the tenement—

(a) under a lease for a life or lives in being (either without a term of years or with a concurrent term of which less than twenty-five years are unexpired), or

(b) under a lease for a term of which less than twenty-five years are unexpired at the date of the service of such notice, or

(c) under a tenancy from year to year or any lesser tenancy,

the landlord shall, within one week, serve the notice or a copy thereof on his immediate superior landlord, endorsed with a statement of the date on which the notice was served on him, and the superior landlord may, within one month after the date of the service of the improvement notice by the tenant on the landlord, serve on the landlord and on the tenant either an improvement consent or an improvement objection.

(5) Every superior landlord on whom an improvement notice or a copy thereof is served under this section (including this subsection) and who holds the tenement—

(a) under a lease of which less than twenty-five years are unexpired at the date of such service, or

(b) under a tenancy from year to year or any lesser tenancy,

shall, within one week, serve the improvement notice or a copy thereof as endorsed under subsection (4) on his next superior landlord, and that superior landlord shall have the like right of serving an improvement consent or an improvement objection as the first-mentioned superior landlord has under this section.