Magistrates' Court General Civil Procedure Rules 2020

any person who is not a proper or necessary party, whether or not that person was one originally, cease to be a party;

any of the following persons be added as a party—

a person who ought to have been joined as a party or whose presence before the Court is necessary to ensure that all questions in the proceeding are effectually and completely determined and adjudicated upon;

a person between whom and any party to the proceeding there may exist a question arising out of, or relating to, or connected with, any claim in the proceeding which it is just and convenient to determine as between that person and that party as well as between the parties to the proceeding;

a person to whom subparagraph (b) applies be substituted for one to whom subparagraph (a) applies.