Book excerpt: A pressing problem often facing commercial practitioners is how to determine the principle which would dictate when a proprietary claim is available and when it is not. This book explains the nature and structure of key interests in property in commercial transactions and analyses the incidence of proprietary claims available to holders of different interests in assets. 0This book is the first to approach the topic of tracing and derived assets in commercial transactions on a principled basis. It subjects an area of little authority and general academic comment to rigorous and detailed analysis. It contains treatment of the relevant case law and discussion of points that have yet to come up in litigation in England and abroad. By way of comparison, it considers salient aspects of the relevant rules under Article 9 of the US Uniform Commercial Code. The book is timely in light of the current debate on the shape of the law reform of secured transactions in England and elsewhere.