The Provisional Adoption Order was a legal loop-hole introduced into adoption legislation by the Conservative government led by Harold Macmillan.  Under British law only British citizens domiciled in Great Britain could adopt British children.  The Adoption Act 1958 did not change this but allowed for non-domiciled individuals to gain permission to legally remove a British child from Britain for the purpose of adoption under a different legal system.

Permission was necessary as a means of controlling the situation and was laid out in the Act

Section 52

(1) Except under the authority of an order under section fifty-three of this Act (Provisional Adoption Order), it shall not be lawful for any person to take or send an infant who is a British subject out of Great Britain to any place outside of the British Islands with a view to the adoption of the infant (whether in law or in fact) by any person not being a parent or guardian or relative of the infant; and any person who takes or sends an infant out of Great Britain to any place in contravention of this subsection, or makes or takes part in any arrangements for transferring the care and possession of an infant to any other person for that purpose, shall be liable on summary conviction to imprisonment for a term not exceeding six months or to a fine not exceeding one hundred pounds or both.

While the application process was similar to that of adoption, two things were different.  1) the length of time required for the observation of the family by social services was six months rather than three and 2) the adopters were required to provide documentary evidence that they were eligible to adopt in the country they proposed to adopt in.  Once the court was satisfied, a Provisional Adoption Order giving permission to remove the child from the UK was granted.

The name is confusing because it contains the word adoption which signifies to anyone hearing the word, permanence and security.  The word should have been transport, a Provisional Transport Order as all the order does is give permission to transport a child out of the UK anywhere, without any checks or safeguards, the very thing that the word adoption promised.  In 1976, the Provisional Adoption Order together with the Adoption Act 1958 was repealed.