(1)In this Part “terrorist” means a person who—
(a)has committed an offence under any of sections 11, 12, 15 to 18, 54 and 56 to 63, or
(b)is or has been concerned in the commission, preparation or instigation of acts of terrorism.
(2)The reference in subsection (1)(b) to a person who has been concerned in the commission, preparation or instigation of acts of terrorism includes a reference to a person who has been, whether before or after the passing of this Act, concerned in the commission, preparation or instigation of acts of terrorism within the meaning given by section 1.