“71. Such hypothetical purchasers will accordingly recognise, when deciding how much to bid for the freeholder’s interest, that there may be a justification to bid more for the freeholder’s interest than the sum which represents the value of the freeholder’s interest calculated on the basis that the Building will remain as flats. In deciding whether in fact to bid more in this manner a hypothetical purchaser would be likely to seek advice as to the risks that the hypothetical purchaser might not be able to carry out the proposed redevelopment at the end of the headlease because of identifiable potential problems, these here being the risk of being unable to obtain vacant possession of one (or both) of the Basement Flat and Flat 1 at the end of the headlease or within a reasonable time thereafter and the risk of having to pay to the lessee of Flat 1 compensation which included a ransom value, and also the risk of being unable to obtain any necessary planning permission .” 207. Where development hope value was assessed, as it was by Mr Buchanan, on the basis that it would be capable of being realised only at the expiry of the leases to which the freehold interest was subject, it was referred to before us as “development value on reversion”