Despite continuing interest in English and Welsh youth justice policy there has been little critical engagement with the nature of policy itself. Instead, analyses share a common methodological position whereby ‘policy’ is equated with policy ‘products’ (such as legislation or ministerial speeches). This article argues that to understand youth justice policy a wider view is required of what constitutes policy, and where and by whom it is made. It explores how policy is produced in the complex arena of social practice which, following the establishment of the Youth Justice Board for England and Wales (YJB), now constitutes the central operation of the system. Through the creation of the YJB the central youth justice system became essentially undefined. This not only gave YJB officials significant influence in shaping the direction of the youth justice system, but a broad and flexible arena in which to act. Moreover it enabled them to do so according to values and objectives potentially unconnected to ministerial outcomes. Drawing on an ethnographic study of the operation of the YJB, this article explores the policy-making work of YJB officials through the transformation of the role and activities of the YJB itself, comparing the initial parameters of its operation to the way it was defined in action. The article discusses the implications for understanding New Labour’s English and Welsh youth justice policy, and the nature of ‘policy’ itself.