s 286 General rule as to what is the relevant interest
(1) The relevant interest in relation to any qualifying expenditure is the interest in the building to which the person who incurred the expenditure on the construction of the building was entitled when the expenditure was incurred. (2) Subsection (1) is subject to the following provisions of this Chapter and to sections 342 (highway undertakings) and 359 (provisions applying on termination of lease). (3) If— (a) the person who incurred the expenditure on the construction of the building was entitled to more than one interest in the building when the expenditure was incurred, and (b) one of those interests was reversionary on all the others, the reversionary interest is the relevant interest.