9. When any question arises, either in connection with the matters hereinbefore referred to, or otherwise, as to whether any person is a member of any such body as aforesaid, or as to the validity of any appointment under this Act, any person interested in such question may apply by petition to the ¹[High Court Division] for its opinion on such question. A copy of such petition shall be served upon, and the hearing thereof may be attended by, such other person interested in the question as the Court thinks fit. Any opinion given by the Court on an application under this section shall be deemed to have the force of a declaratory decree. The costs of every application under this section shall be in the discretion of the Court.