17For the purposes of sections 21 and 22 of the [1984 c. 60.] Police and Criminal Evidence Act 1984 (seized material: access, copying and retention)—
(a)a terrorist investigation shall be treated as an investigation of or in connection with an offence, and
(b)material produced in pursuance of an order under paragraph 5 shall be treated as if it were material seized by a constable.