18.—(1) The Board may require a police officer to retire on the date on which, having considered all the relevant circumstances, advice and information available to them, they determine that he ought to retire on the ground that he is permanently disabled for the performance of the ordinary duties of a member of the police service.
(2) A retirement under paragraph (1) shall be void if, after that date, on an appeal against the medical opinion on which the Board acted in determining that he ought to retire, the appeal board decides that the appellant is not permanently so disabled.
(3) This paragraph applies to a police officer who is permanently disabled for the performance of the ordinary duties of a member of the police service but who, in accordance with a determination of the Board in the circumstances of his case, continues to serve as such.
(4) In respect of a police officer to whom paragraph (3) applies, the Board may consider, at such times as they may in their discretion determine, whether the disablement has ceased, significantly worsened or significantly improved.
(5) If on any such consideration the Board, having considered all the relevant circumstances, advice and information available to them, determine that the officer ought to retire on the ground that he is permanently disabled for the performance of the ordinary duties of a member of the police service they shall require him to retire under paragraph (1) (subject to paragraph(2)).