How have courts interpreted the principle of "good conscience” in the context of an action for the return of an unsecured loan?

In Bank of Montreal v. The King et al. (1906), 1907 CanLII 29 (SCC), 38 S.C.R. 258, 27 C.L.T. 226, Idington J. at p. 280 stated the same principle as follows: “Let us bear in mind that the action for money had and received by means of which this right has usually been asserted, rests upon the principle that primâ facie it is against equity and good conscience that the party who received it should retain it, and remember further that in many instances this primâ facie case is answered by virtue of conditions existing at the time of payment, or subsequent events creating, so to speak, a countervailing equity that would make it against equity and good conscience to insist on the return of the money.”