The Commissioner may cause any explosive which is stored in a depot to be destroyed-
(a) if in his opinion the condition of the explosive is such as to threaten the safety of a depot or of any persons therein; or
(b) if any fee payable under regulation 12 for the storage of the explosive has not been paid and the Commissioner is unable to sell the explosive under paragraph (3) of that regulation within 6 months after the fee becomes due.