"Inequality of bargaining power" is another term used to express essentially the same idea for the same area of law, which can in turn be further broken down into cases on duress, undue influence and exploitation of weakness.
In these cases, where someone's consent to a bargain was only procured through duress, out of undue influence or under severe external pressure that another person exploited, courts have felt it was unconscionable (i.e., contrary to good conscience) to enforce agreements.
Any transfers of goods or money may be claimed back in restitution on the basis of unjust enrichment subject to certain defences.
He called the concept "inequality of bargaining power", while the American case espousing an equivalent doctrine, Williams v. Walker-Thomas Furniture Co. (1965),[3] termed the issue one of "unconscionability".
Note that even though it is accepted that an "inequality of bargaining power" is relevant to the doctrine of undue influence, Lord Denning's broader dictum on a general equitable principle of an "inequality of bargaining power" was later rejected by the House of Lords in the 1985 case National Westminster Bank plc v Morgan.