This book analyses how the system of immigration judicial reviews works in practice, as an area which has, for decades, constituted the majority of judicial review cases and is politically controversial. Drawing upon extensive empirical research and unprecedented research access, it explores who brings judicial review challenges against immigration decisions and why, the type of immigration decisions that are challenged, how cases proceed through the judicial review process, how cases are settled out of court, and how judicial review interacts with other legal and non-legal remedies. It also examines the quality of immigration judicial review claims and the quality of the initial administrative decisions being challenged. Through developing a novel account of the operation of the immigration judicial review system in practice and the lived experience of it by judges, representatives, and claimants, this book adds a significant new perspective to the wider understanding of judicial review.