15. The justices present may appoint one of their number to preside in court to deal with any case in the absence of a justice entitled to preside under rule 4, if—
(a)before making such an appointment, the justices present are satisfied as to the suitability for this purpose of the justice proposed; and
(b)the justice proposed has completed or is undergoing a chairman training course in accordance with rules made under section 18 of the Courts Act 2003, unless by reason of illness, circumstances unforeseen when the justices to sit were chosen, or other emergency no such justice is present.