77 Sir Frederick Jordan in his Chapters on Equity in New South Wales, (6th ed, 1947) p 138 wrote that the relationship of principal and agent is not per se one of influence, citing In Re Coomber. The relation of "confidential agent and his principal" was listed as one of the relationships of presumed influence by Salmond J in Brusewitz v Brown [1923] NZLR 1106 at 1110. Meagher, Gummow and Lehanes's Equity Doctrines and Remedies (4th ed, 2002) at [15-100] consider in this context that "[w]hether an agent-principal relationship is one of influence as well as fiduciary will depend upon the particular case" (citing Moxon v Payne (1873) LR 8 Ch App 881 which, however, was a case where a sale was set aside for fraud of the "gravest character").
78 If the parties are not on equal terms, that is a relevant consideration when determining whether the presumption of undue influence arises. In Brusewitz v Brown [1923] NZLR 1106 at 1110 Salmond J addressed the rule concerning a presumption of undue influence as follows:
The rule is illustrated by transactions between a trustee and his beneficiary, between a solicitor and his client, between a medical man and his patient, between a parent or person in loco parentis and a child who has recently attained his majority, between a guardian and a recently emancipated ward, between a confidential agent and his principal, between a priest and a person under his spiritual influence or domination, between a nun and her religious superior. The generality of the rule, however, and the fact that it is not limited to any closed list of recognized legal relationships, are best shown by the fact that it applies even to a case where the suspected relationship is merely that between a poor and ignorant grantor and a grantee of means and education. Thus in Baker v Monk (4 DeG J & S 388) a transaction was on this principle set aside whereby an old woman in a humble station of life sold to a substantial tradesman a small freehold in consideration of an inadequate annuity. Knight Bruce, L J., says:
The question is whether - to repeat an expression used in several cases - the parties to the transaction were on equal terms. The purchaser was a substantial tradesman. The vendor was a single woman in humble life, of slender education, between sixty and seventy years of age, unprotected and unaided After some little chaffering, as I have said, she consented to accept this weekly payment during her life as the purchase money of the fee-simple. This transaction takes place between this gentleman and this poor woman without the intervention on her part of any other person. …The purchaser and vendor were in such relative positions as that, according to the known established doctrine of this Court, it lies on the purchaser to show affirmatively that the price he has given is the value.
79 The weight and nature of the burden of proof of rebuttal of the presumption was expressed strongly by Isaacs J in Watkins v Combes (1922) 30 CLR 180 at 193 - 194, citing with approval a passage in the judgment of the Privy Council in Poosathurdi v Kanappa Chettiar (1919) LR 47 IA.,1; which included the following: "the person in a position to use his dominating power has the burden thrown upon him, and it is a heavy burden, of establishing affirmatively that no domination was practised so as to bring about the transaction, but that the grantor of the deed was scrupulously kept separately advised in the independence of a free agent".