‘(1) Where a person is committed under section 9 above and is not discharged by order of the High Court…the Secretary of State may by warrant order him to be returned unless his return is prohibited, or prohibited for the time being, by this Act, or the Secretary of State decides under this section to make no such order in his case… (3) An order for return shall not be made in the case of a person who is serving a sentence of imprisonment or detention…in the United Kingdom …until the sentence has been served…’