Personal data are exempt from the provisions of Part II of this Act and of sections 21 to 24 above if the exemption is required for the purpose of safeguarding national security.

Any question whether the exemption mentioned in sub-section (1) above is or at any time was required for the purpose there mentioned in respect of any personal data shall be determined by a Minister of the Crown; and a certificate signed by a Minister of the Crown certifying that the exemption is or at any time was so required shall be conclusive evidence of that fact.

Personal data which are not exempt under subsection (1) above are exempt from the non-disclosure provisions in any case in which the disclosure of the data is for the purpose of safeguarding national security.

For the purposes of subsection (3) above a certificate signed by a Minister of the Crown certifying that personal data are or have been disclosed for the purpose mentioned in that subsection shall be conclusive of that fact.

A document purporting to be such a certificate as is mentioned in this section shall be received in evidence and deemed to be such a certificate unless the contrary is proved.

The powers conferred by this section on a Minister of the Crown shall not be exercisable except by a Minister who is a member of the Cabinet or by the Attorney General or the Lord Advocate.