12.—(1) An enforcement notice may specify in greater detail the measures which are described in general terms in those provisions of the security directive which impose the general requirements, but may not impose any requirement which could not have been imposed by a security directive under the provision under which the security directive was issued.
(2) An enforcement notice may be framed so as to afford the person on whom it is served a choice between different ways of complying with the specified general requirements of the security directive.
(3) In serving an enforcement notice which relates to a security directive, the Commissioner shall specify in the enforcement notice such period as appears to be reasonably required for taking the measures specified in the enforcement notice; and the enforcement notice shall not take effect before the end of the period so specified.
(4) An enforcement notice requiring a person not to cause or permit anything to be done shall be construed as requiring him to take all such steps as in any particular circumstance are practicable and necessary to prevent that thing from being done.