Leasehold Reform, Housing and Urban Development Act 1993

3 (1) The diminution in value of the landlord’s interest is the difference between—

(a) the value of the landlord’s interest in the tenant’s flat prior to the grant of the new lease; and

(b) the value of his interest in the flat once the new lease is granted.

(2) Subject to the provisions of this paragraph, the value of any such interest of the landlord as is mentioned in sub-paragraph (1)(a) or (b) is the amount which at the valuation date that interest might be expected to realise if sold on the open market by a willing seller (with the tenant not buying or seeking to buy) on the following assumptions—

(a) on the assumption that the vendor is selling for an estate in fee simple or (as the case may be) such other interest as is held by the landlord, subject to the relevant lease and any intermediate leasehold interests;

(b) on the assumption that Chapter I and this Chapter confer no right to acquire any interest in any premises containing the tenant’s flat or to acquire any new lease;

(c) on the assumption that any increase in the value of the flat which is attributable to an improvement carried out at his own expense by the tenant or by any predecessor in title is to be disregarded; and

(d) on the assumption that (subject to paragraph (b)) the vendor is selling with and subject to the rights and burdens with and subject to which the relevant lease has effect or (as the case may be) is to be granted.

(3) In sub-paragraph (2) “the relevant lease” means either the tenant’s existing lease or the new lease, depending on whether the valuation is for the purposes of paragraph (a) or paragraph (b) of sub-paragraph (1).

(4) It is hereby declared that the fact that sub-paragraph (2) requires assumptions to be made as to the matters specified in paragraphs (a) to (d) of that sub-paragraph does not preclude the making of assumptions as to other matters where those assumptions are appropriate for determining the amount which at the valuation date any such interest of the landlord as is mentioned in sub-paragraph (1)(a) or (b) might be expected to realise if sold as mentioned in sub-paragraph (2).

(5) In determining any such amount there shall be made such deduction (if any) in respect of any defect in title as on a sale of that interest on the open market might be expected to be allowed between a willing seller and a willing buyer.

(6) The value of any such interest of the landlord as is mentioned in sub-paragraph (1)(a) or (b) shall not be increased by reason of—

(a) any transaction which—

(i) is entered into on or after the date of the passing of this Act (otherwise than in pursuance of a contract entered into before that date), and

(ii) involves the creation or transfer of an interest superior to (whether or not preceding) any interest held by the tenant; or

(b) any alteration on or after that date of the terms on which any such superior interest is held.