This book explores the relationship between the English law of unjust enrichment and legal obligations arising from other branches of the law. It examines the question, primarily, by considering how English courts resolve conflicts between restitution claims and countervailing legal entitlements. This is much needed given recent cases such as IEG v Zurich Insurance and Avonwick Holdings Ltd v Azitio Holdings Ltd clearly showing the differing positions taken by English courts on the question. By applying insights from the theory of unjust enrichment to Anglo-Australian case law, this study gives a welcome cogent explanation of a complex question.