(1) The provisions of section 53(1) have effect in relation to dispositions of property, whether by will or otherwise, and whether made before or after the commencement of the Adoption of Children Act 1964 , except that—
(a) those provisions do not affect a disposition of property by a person who, or by persons any of whom, died before the commencement of that Act; and
(b) those provisions do not affect a disposition of property that took effect in possession before the commencement of that Act.
(2) The provisions of section 53(1) do not apply in relation to an agreement or instrument (not being a disposition of property) made or executed before the commencement of the Adoption of Children Act 1964 .
(3) Where—
(a) before the commencement of the Adoption of Children Act 1964 , a person made, by an instrument other than a will, a disposition of property;
(b) the disposition had not taken effect in possession before the commencement of that Act; and
(c) it did not appear from the instrument that it was the intention of that person to include adopted children as objects of the disposition—
that person may, notwithstanding that the instrument could not, apart from this subsection or a corresponding previous enactment, be revoked or varied, by a like instrument vary the first-mentioned instrument to exclude adopted children (whether adopted under this Act or otherwise) from participation in any right, benefit or privilege under the instrument.
(4) In relation to a disposition of property by a person who, or by persons any of whom, died before the commencement of the Adoption of Children Act 1964 an adoption order made under that Act or this Act shall have effect as if neither that Act nor this Act had been passed.
(5) Nothing in section 53 or in this section affects the operation of any provision in a will or other instrument (whether made or coming into operation before or after the commencement of this Act) that expressly distinguishes a beneficiary or class of beneficiaries from another beneficiary or class.