8(1)In any proceedings under section 25, a certificate signed by or on behalf of a Minister of the Crown and certifying—E+W+S+N.I.
(a)that any conditions or requirements specified in the certificate were imposed by a Minister of the Crown and were in operation at a time or throughout a time so specified, or
(b)that an act specified in the certificate was done for the purpose of safeguarding national security,
shall be conclusive evidence of the matters certified.
(2)A document purporting to be such a certificate shall be received in evidence and, unless the contrary is proved, be deemed to be such a certificate.