Book excerpt: The language of duress and necessity is found in crime, tort and contract. This book explores those pleas, in both case law and theory, across the subject boundaries, and across jurisdictions. In doing so, it seeks to identify the lessons which each area of law can learn from the others, and to tease out common themes while demarcating important differences. The overall outcome is a law more coherent and understood in sharper detail. This book considers the law of England and Wales, Australia, New Zealand, Hong Kong and Canada, as well as the American tortious defence of necessity.