11.—(1) Subject to paragraph (2), the Secretary of State for Defence may, by a certificate in writing, exempt any person or class of persons from regulation 6(4) in respect of activities carried out in the interests of national security which conflict with the requirements of that paragraph, and any such exemption may be granted subject to conditions and to a limit of time and may be revoked by a certificate in writing at any time.
(2) The Secretary of State shall not grant any such exemption unless he is satisfied that the health and safety of the employees concerned is ensured as far as possible in the light of the objectives of these Regulations.