ABSTRACT
Mistake in the context of vitiation of a contract has a restricted meaning. The uncertainly surrounding the doctrine of mistake, which arises from conflicting case law, is exacerbated by a difference of opinion amongst academics as to the correct terminology for different types of mistake recognised by the common law. Glanville Williams has argued that mistakes as to quality cannot be separated from mistakes as to substance and that qualities considered together produce the essence of an article. Mutual mistake refers to the situation where the parties are at cross-purposes. The House of Lords ordered that the defendant should have a lien on the property for the cost of improvements to the fishery as, otherwise, the plaintiff would have been unjustly enriched by the defendant's mistaken expenditure. Accordingly, when a mistake has been made which falls short of an operative mistake at common law, equity may still refuse to enforce the agreement, when this would be unfair to the defendant.
