(1) This rule applies only to proceedings about —
(a) the construction of a written instrument;
(b) the estate of someone who is deceased; or
(c) property subject to a trust.
(2) The court may appoint one or more persons to represent any person or class of persons (including an unborn person or persons) who is or may be interested in or affected by the proceedings (whether presently or for any future, contingent or unascertained interest) where —
(a) the person, or the class or some member of it, cannot be ascertained or cannot readily be ascertained;
(b) the person, or the class or some member of it, though ascertained cannot be found; or
(c) it is expedient to do so for any other reason.
(3) An application for an order to appoint a representative party under this rule may be made by any —
(a) party; or
(b) person who wishes to be appointed as a representative party.
(4) A representative appointed under this rule may be either a claimant or a defendant.
(5) A decision of the court binds everyone whom a representative claimant or representative defendant represents in that capacity.