21.—(1) A chief officer of police may revoke an explosives certificate which that chief officer of police has issued if, at any time, that chief officer of police is satisfied that the holder was not when the explosives certificate was issued, or is no longer, a fit person to hold an explosives certificate in the terms of that explosives certificate.
(2) A chief officer of police must revoke an explosives certificate which that chief officer of police has issued if, at any time, that chief officer of police is satisfied that any of the conditions in paragraph (1) or (2) of regulation 19 was not met when the explosives certificate was issued, or is no longer met.
(3) An explosives certificate ceases to be valid—
(a)5 years after the date of issue; or
(b)after such lesser time as may be stated therein; or
(c)after notice of revocation by the chief officer of police for the relevant police force has been served on the holder of the certificate,
whichever happens first.
(4) The holder of an explosives certificate must surrender it to the chief officer of police who issued it immediately after a notice of revocation has been served on that holder under paragraph (3)(c).