considered in Australian cases. The Australian Acts presuppose the existence of Commissions appointed under prerogative or inherent executive powers and merely confer ancillary powers of compelling evidence and the like. Under Acts of that type the validity of the Commission depends on the common law and the division of powers in the Australian Constitution. Under the New Zealand Act a Commission can be given a statutory source for its basic authority even if it is a Royal Commission and has a prerogative source as well. The Erebus Commission was appointed to inquire into the causes and circumstances of the crash. Among the particular questions referred to it was: (g) Whether the crash of the aircraft or the death of the passengers and crew was caused or contributed to by any person (whether or not that person was on board the aircraft) by an act or omission in respect of any function in relation to the operation, maintenance, servicing, flying, navigation, manoeuvring, or air traffic control of the aircraft, being a function which that person had a duty to perform or which good aviation practice required that person to perform? All the terms of reference fall well within s. 2 (e). The Commission was not appointed to inquire into allegations of crime so we are not now called upon to go into the question whether a Royal Commission can be appointed for such a purpose, on which New Zealand and Australian authorities diverge (see _In re The Royal Commission on Licensing_ (1945) N.Z.L.R. 665, 679; and D.R. Mummery "Due Process and Inquisitions", 97 L.Q.R. 287). Nevertheless paragraph 377 of the Royal Commission Report contains findings of organized perjury. The judgment in the leading New Zealand case, _Cock_ v. _Attorney-General_, while denying that the prerogative can authorize a Commission with the main object of inquiring into alleged crimes, recognizes at p. 425 that a Commissioner may investigate an alleged crime if to do so would be "merely incidental to a legitimate inquiry and necessary for the purpose of that inquiry". We think that the test must be what is reasonably incidental to valid terms of reference. In relation to paragraph 377 the allegation of excess of jurisdiction turns accordingly on whether the findings are reasonably incidental to an inquiry into the causes and circumstances of the crash.