Southern Foundries (1926) Ltd v Shirlaw [1940] AC 701 is an important English contract law and company law case. In the field of contracts it is well known for MacKinnon LJ's decision in the Court of Appeal, where he put forth the "officious bystander" formulation for determining what terms should be implied into agreements by the courts. In the field of company law, it is known primarily to stand for the principle that damages may be sought for breach of contract by a director even though a contract may de facto constrain the exercise of powers to sack people found in the company's constitution.