“Where a party inadvertently allows a privileged document to be inspected, the party who has inspected the document may use it or its contents only with the permission of the court.”
“… it might be or appear dangerous or misleading to allow the plaintiffs to disclose part of the memorandum and to assert privilege over the remainder”
“i) What might be called a 'true' waiver occurs if one party either expressly consents to the use of privileged material by another party or chooses to disclose the information to the other party in circumstances which imply consent to its use. Such a waiver may be either general or limited in scope. ii) Where a party waives privilege in the above sense by deliberately deploying material in court proceedings, the party also loses the right to assert privilege in relation to other material relating to the same subject matter: see e.g. Great Atlantic Insurance Co. v Home Insurance Co.[1981] 1 WLR 529 . The underlying principle is one of fairness to prevent 'cherry picking': see e.g. Brennan v Sunderland City Council[2009] ICR 479 , 483-4 at [16]. iii) Similarly, a party who by suing its legal advisor puts their confidential relationship in issue cannot claim privilege in relation to information relevant to the determination of that issue. Again, the governing principle is one of fairness: see e.g. Paragon Finance v Freshfields[1999] 1 WLR 1183 . iv) Because privilege only protects information which is confidential, if the information concerned ceases to be confidential, privilege cannot be claimed. Where a party does an act which has the effect of making information public, this has sometimes been described as a waiver of privilege (see e.g. Goldstone v Williams(1899) 1 Ch 47 ), but it is more accurate to say that privilege cannot be claimed because confidentially has been lost. v) Where a party comes into possession of privileged material by any means, and even if without the knowledge or consent of the other party, the receiving party is free to use such material subject to the equitable jurisdiction of the court to restrain a breach of confidence.”