while he is confined in or being taken to or from any prison in which he may be lawfully confined; or

while he is working or is, for any other reason, outside the prison in the custody or under the control of an officer of the prison F2 , a constable (“constable” having the same meaning as it has, by virtue of paragraph 17(1) and (2) of Schedule 1 to the Crime (Sentences) Act 1997 (c. 43), in section 40(1) of this Act) or a police custody and security officer ; or

while he is being taken to any place to which he is required or authorised by or under this Act to be taken; or

while he is kept in custody in pursuance of such requirement or authorisation.