Air Navigation Order Article 72 Fatigue of crew - operator's responsibilities:-
(2) The operator of an aircraft to which this article applies shall not cause or permit any person to fly therein as a member of its crew if he knows or has reason to believe that the person is suffering from, or, having regard to the circumstances of the flight to be undertaken, is likely to suffer from, such fatigue while he is so flying as may endanger the safety of the aircraft or of its occupants.
Air Navigation Order Article 73 Fatigue of crew - responsibilities of crew:-
(1) A person shall not act as a member of the crew of an aircraft to which this article applies if he knows or suspects that he is suffering from, or, having regard to the circumstances of the flight to be undertaken, is likely to suffer from, such fatigue as may endanger the safety of the aircraft or of its occupants.