14. Protecting the public interest

This chapter examines how English law deals with contracts against the public interest under the doctrine of illegality. The doctrine of illegality reflects a broader principle that applies across private law, that legal actions cannot be founded on illegal acts. In contract law, its implication is that contracts contrary to law or public policy are void. The chapter first considers the problem of illegal behaviour in contracting before discussing the rule-based approach to illegality and its limits. It then reviews the Supreme Court decision in Patel v Mirza and how it gave rise to the ‘range of factors’ approach to illegality. It also looks at criteria that make a contract illegal, including cases where the illegality consisted of criminal and civil wrongs. The chapter concludes with an overview of other types of illegality, such as the ‘injurious to good government’ ground and restraint of trade.