The tribunals system in England and Wales has been transformed by the entry into force of the Tribunals, Courts and Enforcement Act 2007; among other things, tribunals are now located more firmly and explicitly than ever before within the judicial branch. Questions concerning the relationship between tribunals and regular courts fall to be confronted afresh within this new institutional landscape. Those questions form the focus of this article, which is particularly concerned with the issue recently considered by the Supreme Court in Cart whether, and if so to what extent, decisions taken within the tribunals system (by the Upper Tribunal) should be susceptible to judicial review by the High Court. In Cart, emphasis was placed upon the concept of “proportionate dispute resolution” as a means by which to delimit regular courts' oversight of tribunals' decisions, raising fundamental questions both of legal doctrine (relating to the relevance of the orthodox doctrinal tools of administrative law) and legal policy (concerning the degree of error on the part of a tribunal that a higher court should tolerate in the interests of the efficient, or proportionate, use of judicial resources).