Questions of agency regularly arise in the work of commercial practitioners. Agency: Law and Principles, now in its fifth edition, addresses these questions by offering a clear and accessible analysis of the principles of agency law and the concept of agency. Forensic analysis of the most up-to-date case law is combined with a practical approach to the law which accurately reflects modern commercial realities, considering the application of agency principles according to particular classes of agents operating in the major commercial sectors. Areas discussed include actual and apparent authority of an agent, agency of necessity, sub-agency and termination of agency, want of authority and ratification looking at the legal relations between principal and agent, as well as the relations between agent and third party. This fifth edition has been fully updated to include all significant new case law and legislation, including the Supreme Court decisions in Barton v Morris [2023] AC 684, Philipp v Barclays Bank UK Plc [2024] AC 346, and Rukhadze v Recovery Partners GP Ltd [2025] 2 WLR 529. A new section has been added on agency and attribution in the context of company law. As algorithmic agreements via electric platforms complicate the concept of agency, consideration has been given to the relevance of the law of agency in this context, too. This clearly written, authoritative, and concise work on the law of agency is essential reading for all commercial lawyers.