In an era of rapid technological, economic and political change, we want financial regulation to be adaptable. But how are we to understand adaptability and how are we to integrate it into practice? Drawing on Ronald Dworkin's legal theory, Adaptable Financial Regulation: Theory, Policy and Practice challenges the conventional view that equates adaptability with legal flexibility, and instead develops a theory of adaptable financial regulation that conceives adaptability as a virtue of good public governance, requiring that adaptations emerge from principled reasoning oriented toward justice.Effective regulation, this book contends, is not simply about making rules that can adapt but about interpreting rules so that they can adapt in the right way, ensuring that adjustments in action serve the core values and purposes of financial regulation. Recognizing that the legal constitution of financial regulation imposes a degree of discipline on how adaptation occurs, the book further argues for an architecture of interpretive practice in financial regulation characterized by principled reasoning, constructive contestation, and accountability mechanisms that enable meaningful third-party scrutiny. Applying this theory across the UK, the EU, and international contexts, the book examines three central themes: rulebook design, supervisory approach, and accountability structures. It provides a diagnosis of the current state of adaptable financial regulation, identifies practical challenges, and proposes pathways for improvement and future development. Ultimately, the book advances a framework for analysis and regulatory design in which adaptability is treated as a central virtue of financial markets governance aimed at curbing arbitrary rule application and strengthening public trust. It also brings to light the deeper questions of justice that financial regulators confront in executing their technocratic functions, urging that these be recognised and debated for what they are: as matters of principle and not as questions of political power alone.