In what circumstances will solicitor-client privilege be breached?

In Woodglen, Macdonald J. also stated the following in noting that not every solicitor-client communication that goes to the “heart of the matter” is, on that account alone, privileged: … the defendants submit that when the solicitor-client communication goes to the "very heart of the matters at issue" in the litigation, the solicitor-and-client privilege cannot be maintained. In my view, this is not what the cases stand for. … In Katz v. Lapsker, [1988] O.J. 1950, another case of Master Peppiatt, counsel for the moving party had argued that the solicitor-client privilege had been penetrated because the communications were "at the heart of the matter of the litigation". Master Peppiatt correctly stated the law in this regard as follows: With great respect to [counsel for the moving party], I think that he has misconceived the principle laid down in these cases. It is that the solicitor-client privilege is set aside (as I said, I think this is really a form of waiver) where a party raises the issue of what he learned from his solicitor. It does not mean that where certain information or evidence is central to the litigation, the solicitor can be compelled to reveal what he, or she, said to the client. Such a doctrine would entirely destroy the solicitor-client privilege. In my view, this is an accurate characterization of the issue raised by the defendants in this motion. The cases in this area are based upon waiver where a party puts into issue the instructions given to his or her solicitor. If a litigant were able to obtain information that would otherwise be privileged, on the basis that it goes to the heart of the matter, the concept of solicitor-client privilege would be destroyed. Accordingly, I view the "heart of the matter" concept as being one which is misconceived….