The United Kingdom should now be understood as a counter-terrorist state, that is a state in which counter-terrorism law, policy, discourse, and operations are mainstreamed across the domains of law and government in forms that are conceptualised and designed as ‘permanent’ in at least some cases; in which non-state actors are responsibilised for counter-terrorism; and in which all persons are the subjects of counter-terrorism, although not to equal degrees. This book argues that counter-terrorism review—which it defines as the legal, political, and policy processes that consider the application and impacts of counter-terrorism law and policy in theory as well as in practice, with a view to assessing its merits and contributing towards its improvement—has the capacity to enhance accountability in the counter-terrorist state. Building on exclusive interviews with political actors and practitioners, as well as detailed empirical analysis of existing reviews—it presents the first comprehensive, critical analysis of counter-terrorism review in the United Kingdom. While this reveals substantial pockets of good practice, it also shows that the accountability enhancing potential of counter-terrorism review is limited in practice by executive domination, parliamentary limitations, persistent state secrecy, and the absence of trust in the counter-terrorist state.