PPRUNE Radar Don't know whether this makes much difference to your argument but ‘Appropriate air traffic control unit’ is defined in the ANO as "in relation to an aircraft either the air traffic control unit serving the area in which the aircraft is for the time being, or the air traffic control unit serving the area which the aircraft intends to enter and with which unit the aircraft is required to communicate prior to entering that area, as the context requires". The phrase "with which unit the aircraft is required to communicate" might be a problem but I agree that it all comes down to an interpretation.