“The true analysis of what the courts are doing in such cases of so-called implied waiver of privilege is, in my judgment, to prevent the unfairness which would arise if the plaintiff were entitled to exclude from the court’s consideration evidence relevant to a defence by relying upon the privilege arising from the solicitor’s duty of confidence. The client is thus precluded from both asserting that the solicitor has acted in breach of duty and thereby caused the client loss and, to make good that claim, opening up the confidential relationship between them and at the same time seeking to enforce against that same solicitor a duty of confidence arising from their professional relationship in circumstances where such enforcement would deprive the solicitor of the means of defending the claim. It is fundamental to this principle that the confidence which privilege would otherwise protect arises by reason of the same professional relationship between the parties to the litigation. The underlying unfairness which the principle aims to avoid arises because the claim is asserted and the professional relationship opened for investigation against the very party whose duty of confidence is the basis of the privilege. It is against the unfairness of both opening the relationship by asserting the claim and seeking to enforce the duty of confidence owed by the defendant that the principle is directed.”