"The present case is one in which quite clearly if the evidence did establish a propensity in the defendant occasionally to molest young female patients in the course of dental examination, that did make it more likely that he had committed the several offences charged. We do not understand Mr Coker to submit otherwise. Of course, where propensity is advanced by way of multiple complaints, none of which has yet been proved, and whether they are proved or not is the question which the jury must answer, that is a different case from the case where propensity is advanced through proof of a previous conviction which may be incapable of contradiction."