69Evidence
(1)Any finding by a court under section 19 or 20 of the [1968 c. 71.] Race Relations Act 1968, or by a court or industrial tribunal under this Act, in respect of any act shall, if it has become final, be treated as conclusive in any proceedings under this Act.
(2)In any proceedings under this Act a certificate signed by or on behalf of a Minister of the Crown and certifying—
(a)that any arrangements or conditions specified in the certificate were made, approved or imposed by a Minister of the Crown and were in operation at a time or throughout a period 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.
(3)A document purporting to be a certificate such as is mentioned in subsection (2) shall be received in evidence and, unless the contrary is proved, shall be deemed to be such a certificate.