Healthcare professionals are expected to deliver care that is consistent with clinical guidelines. In this article, we show that the English courts are increasingly willing to be persuaded by written guidelines when determining the standard of care in cases of alleged clinical negligence. This reflects a wider shift in the approach taken by courts in a number of common law jurisdictions around the world. However, we argue that written guidelines are still only one element that courts should consider when determining the standard of care. It is possible to deliver perfect care that deviates from professional guidelines and even to deliver negligent care by uncritically following a guideline that is flawed. We further argue that written guidelines are relevant beyond defining the accepted standard of care. This is because the decision to deviate from a guideline suggests the existence of multiple approaches that should be discussed with patients as part of ensuring informed consent. It is therefore likely that written guidelines will become an even more prominent feature of the medicolegal landscape in future years.