18(1)If on a complaint under paragraph 17 above it is shown that the action to which the complaint relates was taken for the purpose of safeguarding national security, the industrial tribunal shall dismiss the complaint.
(2)A certificate purporting to be signed by or on behalf of a Minister of the Crown, and certifying—
(a)that action specified in the certificate was taken for the purpose of safeguarding national security, or
(b)that a particular request for information could not be complied with except by disclosing information the disclosure of which would have been against the interests of national security,
shall for the purposes of this Schedule be conclusive evidence of the fact so certified.