This book offers a new interpretation of judicial review in England and Wales as being concerned with the advancement of justice and good governance, as opposed to being concerned primarily with ultra vires or common law constitutionalism. It is developed both from examining the functions and values that ought to be served by judicial review, and from analysis of empirical 'social' facts about judicial review primarily as experienced in the Administrative Court. Based on ground-up case law analysis it constructs a new taxonomy on the grounds of judicial review: mistake, procedural impropriety, ordinary common law statutory interpretation, discretionary impropriety, relevant/irrelevant considerations, breach of an ECHR protected right or equality duty, and constitutional allocation of powers, constitutional rights, or other complex constitution principles. It explains each of these grounds, what academic and judicial support there might be for them outside case law analysis, and their similarities and differences when viewed against popular existing taxonomies.