(4) Where, by virtue of paragraph (b) of Subsection (1) of this Section or of the last foregoing Subsection, the right to receive a value payment or share of a value payment becomes vested in the person by whom an interest in land is acquired, whether compulsorily or by agreement, the amount of that payment or share (including any interest thereon) shall not exceed the sum paid by that person by way of compensation or consideration in respect of the interest so acquired.—[Mr. Silkin.]