12.—(1) Subject to paragraphs (2) and (3), a member of a police force appointed in the rank of constable, other than such a member who transferred to the force from another police force having completed the required period of probation therein, shall be on probation for such period as the Secretary of State shall determine in respect of such appointments.
(2) In making a determination under paragraph (1), the Secretary of State may, subject to paragraph (3), confer on the chief officer discretion to determine the required period of probation in a particular case.
(3) For the purposes of a determination under paragraph (1), the periods to be counted or disregarded in reckoning service shall be such as may be determined by the Secretary of State.