In determining the amount of compensation or purchase money payable to any person in respect of an interest in land acquired under this Act in a case where—
(a)the person has an interest in any other land contiguous with or adjacent to the land so acquired; and
(b)the value of the person’s interest in any such contiguous or adjacent land is enhanced by reason of the works authorised by this Act or any of them,
the amount of the enhancement in value shall be set off against the compensation or purchase money.