'(1) For the purposes of an examination by the Comptroller and Auditor General of a government department's accounts—
(a) he shall have a right of access at all reasonable times to any of the documents relating to the department's accounts, and
(b) a person who holds or has control of any of those documents shall give the Comptroller and Auditor General any assistance, information or explanation which he requires in relation to any of those documents.