This new edition is a fully updated, clear and concise account of the law of unjust enrichment, and attempts to move away from the usage of obscure terminology inherited from the past. It organises modern law around five simple questions: Was the defendant enriched? If so, was it at the claimant's expense? If so, was it unjust? The fourth question is then what kind of right the claimant has and the fifth is whether the defendant has any defenses.