Courts generally defer to any responsible professional opinion, so long as it's reasoning is coherent, and the patient was informed of material risks. 

Bolam applies to both treatment and risk disclosure, except where the risk is novel or not yet studied. 

Courts will only depart from professional opinion if it is both illogical and inconsistent with national guidelines. 

Where expert views conflict, courts prefer the majority unless the doctor reasonably thought non-disclosure was in the patient's best interests. 

Courts may refuse to follow a professional view if its reasoning is not logically defensible, or if the patient was not adequately informed about material risks and alternatives.