The single and comprehensive judgment in R (Bell) v Tavistock and Portman NHS Foundation Trust draws a clear line between matters which can be legitimately considered by the Courts and those medical policy issues which have to be left to doctors, medical policy makers within the NHS and, in the last resort, government. The claim in Bell failed because the Claimant failed to prove the Tavistock Trust was acting unlawfully, and the Court of Appeal sent out a clear message that the Court should not have gone any further by giving guidance to govern future medical practice in the difficult and controversial area of treatment for children presenting with symptoms of gender dysphoria. The Claimant in Bell argued that it was unlawful to treat children presenting with symptoms of gender dysphoria with puberty blockers if specialist medical professionals considered that this was an appropriate medical treatment for that child. That case failed in the High Court and was not revived in the Court of Appeal. Instead, the court gave “guidance” which effectively meant that children under the age of 16 could not consent to puberty blockers and only a Judge of the High Court should decide the consent issue. That position was substantially ameliorated by the decision of the High Court in AB v CD [2021] EWHC 741 (Fam) where the High Court decided that parents of a child could give consent on behalf of the child for puberty blockers in a case where the child’s capacity to give his or her own consent is unclear. Thus the practical difficulties arising from the Bell judgment were largely resolved. However the Court of Appeal has now decided that the High Court was wrong to have strayed into giving “guidance” and should not have made the Declarations about what a child needed to understand to give consent. There are three lessons emerging from the judgment. First, the role of the judicial review Court is limited to decide the lawfulness of the actions of public bodies in individual cases based on individual facts. The role of the judicial review court is rarely to give generalised guidance affecting cases that are not before the court. That limitation was affirmed by the Court of Appeal in R (Burke) v. General Medical Council [2005] EWCA Civ 1003, [2006] QB 273 is repeated here. Secondly, the Court of Appeal was critical of the High Court in permitting the Claimant to admit “expert” evidence without following the strict rules under CPR 35 which govern the admission of such evidence. Expert evidence can occasionally be properly admissible in judicial review proceedings but the procedural steps are important to ensure that the court only does so when it is properly relevant to the particular case and that there is transparency about who is providing the evidence. This case contains a clear warning to all parties to a judicial review case to strictly follow the rules about the admission of expert evidence. Thirdly, those who have concerns about shortcomings or deficiencies in the way medical practice is carried out have to use the established mechanisms of review through the Trust Complaints Procedures, reviews by the Care Quality Commission or intervention by NHS England, but cannot come to the court to ask the court to give guidance to correct established practices. In this case a CQC report suggested that Trust staff were not always operating consent procedures correctly. However, the Court said: “The fact that the report concluded that Tavistock had, in certain respects, fallen short of the standard expected in its application of the service specification does not affect the lawfulness of that specification; and it would not entitle a court to take on the task of the clinician in determining whether a child is or is not Gillick competent to be referred on to the Trusts or prescribed puberty blockers by the Trusts” The strong message is that the judicial review court will not step in to provide “guidance” where there is no systemic unlawfulness. That is consistent with the message given out by the Court of Appeal in cases such as R (Bayer plc) v. NHS Darlington Clinical Commissioning Group [2020] EWCA Civ 449. David Lock QC acted for some of the Intervenors in Bell and also for the parents in AB v CD. He was instructed in both cases by Anne-Marie Irwin of Rook Irwin Sweeney.