19.1—(1) This rule applies where a party is to be added or substituted except where the case falls within rule 19.4 (special provisions about changing parties after the end of a relevant limitation period(GL)).
(2) The court may order a person to be added as a new party if—
(a)it is desirable to add the new party so that the court can resolve all the matters in dispute in the proceedings; or
(b)there is an issue involving the new party and an existing party which is connected to the matters in dispute in the proceedings, and it is desirable to add the new party so that the court can resolve that issue.
(3) The court may order any person to cease to be a party if it is not desirable for that person to be a party to the proceedings.
(4) The court may order a new party to be substituted for an existing one if—
(a)the existing party’s interest or liability has passed to the new party; and
(b)it is desirable to substitute the new party so that the court can resolve the matters in dispute in the proceedings.