(1)No warder shall, while on duty, at any time, under any circumstances, on any pretext, leave his post or absent himself from duty until relieved in due course and relieved from duty:Provided that he may leave his beat to prevent an escape or to assist in subduing a disturbance taking place within his sight when he is on main wall patrol duty or, when he is in charge of prisoners, if he can do so without serious risk to the safe custody of those prisoners. It rests upon the warder concerned to show that the circumstances were so exceptional as to justify his doing so.
