21(1)A person’s detention shall be periodically reviewed by a review officer.
(2)The first review shall be carried out as soon as is reasonably practicable after the time of the person’s arrest.
(3)Subsequent reviews shall, subject to paragraph 22, be carried out at intervals of not more than 12 hours.
(4)No review of a person’s detention shall be carried out after a warrant extending his detention has been issued under Part III.