This privilege attaches irrespective of where the document originates or in whose custody it is provided it emanated from or came into possession of some servant of the crown; (2) the privilege can be claimed or waived by the authority of the Minister or the head of the department; (3) secondary evidence may not be given of a document for which privilege is established; (4) official correspondence per se is not privileged on the ground of its being confidential or official nor is it a valid ground that production would involve the Government in criticism or expose 'want of efficiency in the administration or open up claims to compensation but the ground for privilege is that the production would be detrimental to the interest of the public or interfere with the efficient working of the public service or it belongs to class of documents which it is the practice of the department to keep secret; (5) the minister 's objection may be conveyed by a letter or by the official who attends at a trial but 436 the court may require an affidavit by or the attendance of the Minister; (6) before a privilege is claimed it is desirable that each document should be examined by the department concerned and inspection permitted of all documents which cannot harm the public interest; (7) if a minister claims privilege the court will accept his statement and ought not to examine the document to see if the objection is well founded; (8) public interest must not be put in jeopardy by the production of a document which could injure it and the court should, if necessary, prohibit the production even though no objection has been taken by the Government department.