How have the courts dealt with conflicts of interest in law?

[33] In MacDonald Estate v. Martin, the facts are accurately set out in the headnote as follows: The respondent was administrator with the will annexed of an estate and brought this action against the appellant and the corporate defendant for an accounting. The respondent was represented by one particular solicitor with the aid of others in the firm. The appellant was originally represented by a solicitor who was later appointed to the bench. That solicitor was assisted by a graduate articled student who later became a junior in the firm. When her principal was appointed to the bench, she left the firm and joined another. Two years later, she and other members of that firm joined the firm representing the respondent, but she was not involved with this litigation. The litigation had been going on for some nine years and was drawing to its conclusion. One discovery was still required, after which the parties expected to be able to set the case down for trial. The appellant brought a motion for a declaration that the respondent’s firm was ineligible to continue to act for the respondent, because of the junior’s conflict of interest. She was on pregnancy leave and the firm undertook, if necessary, to have her work out of her home until the case was finished or cease work for the firm during that time. The respondent wished to retain the particular lawyer who had been her principal as his counsel. He and she filed affidavits showing that no breach of confidence had occurred. The motion was granted at first instance, but an appeal was allowed.