Where a chargeable gain accrues to a person on a disposal of an interest in land to which the principal section applies, being a disposal in relation to which [ paragraph 9 of Schedule 5 to the Capital Gains Tax Act 1979 F3] ( sales of land in United Kingdom reflecting development value) applies, then, if the amount of the gain is by virtue of sub-paragraph (4) of that paragraph computed without regard to [ the said Schedule 5 F3] ( assets held on 6 th April 1965), this Chapter shall have effect in relation to that disposal as if in subsection (3)(c) of the principal section and paragraphs 11 and 12 of this Schedule any reference to the current use value of the interest at the time of its acquisition by the person making the disposal or, if the interest was acquired by him before 6 th April 1965, its current use value at that date referred only to its current use value at the time of its acquisition by him.