"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.

It is difficult to find reasons why the Court should refuse to entertain
that question. While Commissions of mere inquiry and report are largely
free from judicial control, there is strong authority indicating that
the Courts have at least a duty to see that they keep within their terms
of reference. We agree with the opinion of Myers C.J. in the _Royal
Commission on Licensing_ case at p. 680 that it is implicit in all the
judgments in the Privy Council and the High Court in _Attorney-General
for the Commonwealth of Australia_ v. _Colonial Sugar Refining Co. Ltd_
(1914) A.C. 237, 15 C.L.R. 182, that if it can be said in advance that
proposed questions are clearly outside the scope of the inquiry they are
irrelevant and cannot be permitted. In the _Royal Commission on
Licensing_ case that very principle was applied in this Court, it being
held that certain matters were not within the ambit of the Commission's
inquiry. That decision was given on a case stated by the Royal
Commission under ss. 10 and 13 of the 1908 Act, but the _Sugar Company_
case was an action for declaration and injunctions and the procedure was
expressly approved in the judgment of their Lordships delivered by
Viscount Haldane L.C. ((1914) A.C. at 249-50). Similarly in _McGuinness_
v. _Attorney-General_ (1940) 63 C.L.R. 73 the High Court, on an appeal
from a conviction for refusing to answer a question touching the subject
matter of an inquiry by a Commissioner, accepted without any apparent
difficulty that the Court had authority to determine whether the
question was relevant.