In the UK, a medico-legal defence for a clinician accused of failing to provide an acceptable standard of care for a doctor of his or her qualification and experience. The defence is that a responsible body of medical practitioners would have taken the same action, even though others would have acted differently. The precise size of a ‘responsible body’ has not been defined. The test has been modified following a case referred to as Bolitho, in which it was held that the Bolam defence failed if it could be shown that the actions relied upon, although carried out by some responsible doctors, were nonetheless illogical. Also in the case of Montgomery, the UK Supreme Court has ruled that in determining whether a patient has given properly informed consent, the test of the validity of the advice on which he or she has based that decision, is not that of ‘a responsible body of medical practitioners’ but that of ‘a reasonable person in the patient's position’.