“The offence requires, as the third element, that the misconduct must be so serious as to amount to an abuse of the public’s trust in the office holder. It is not in our view sufficient simply to tell the jury that the conduct must be so serious as to amount to an abuse of the public’s trust in the office holder, as such a direction gives them no assistance on how to determine that level of seriousness. There are, we consider, two ways that the jury might be assisted in determining whether the misconduct is so serious. The first is to refer the jury to the need for them to reach a judgment that the misconduct is worthy of condemnation and punishment. The second is to refer them to the requirement that the misconduct must be judged by them as having the effect of harming the public interest.”