12 While Beaumont J in Telstra took a contrary view, the view of the majority was agreed in by a Full Bench of the Federal Court (Ryan, Carr and Marshall JJ) in Perpetual Trustees (WA) Ltd v Equuscorp Pty Limited [1999] FCA 925. In that matter the Full Bench said:
17 In our view, the facts of the present matter reflect the requisite degree of unfairness. Equus complains that it relied on the specified representations when it executed the security document. It says that the words "letter of credit" appearing in that document do not faithfully record the common intention of the parties and that the words were used under a mutual mistake of fact. There is evidence, that at the relevant time or times, i.e. shortly before executing the security document, Equus sought and obtained legal advice. In our opinion, in those circumstances, it would be relevantly unfair for Equus to be allowed to maintain legal professional privilege. Equus' state of mind is central, at the very least, to its claim for rectification - see Ampolex - a case cited with apparent approval by Beaumont J in his dissenting reasons in Telstra.
13 The unfairness to which the Full Court was there referring is that which the law regards as preventing the maintenance of the privilege once the privilege holder's conduct has created that unfairness. The High Court (Gleeson CJ, Gaudron, Gummow and Callinan JJ) in Mann v Carnell (1999) 168 ALR 86 at 94 said:
Waiver may be express or implied. Disputes as to implied waiver usually arise from the need to decide whether particular conduct is inconsistent with the maintenance of the confidentiality which the privilege is intended to protect. When an affirmative answer is given to such a question, it is sometimes said that waiver is "imputed by operation of law" (For example, Goldberg v Ng (1995) 185 CLR 83 at 95; 132 ALR 57). . . . What brings about the waiver is the inconsistency, which the courts, where necessary informed by considerations of fairness, perceive, between the conduct of the client and maintenance of the confidentiality; not some overriding principle of fairness operating at large.