The binding legal principles established are: (1) A party is an 'affected party' under Rule 42(1)(a) entitled to seek rescission of an ex parte order if they have a direct and substantial interest in the subject matter of the order, which interest is sufficient to have entitled them to intervene in the original application. Such interest extends beyond mere financial considerations. (2) A rescission order is not appealable as it lacks the three Zweni attributes required for appealability: it is not final in effect (as it can be revisited by the court that granted it), it is not definitive of parties' rights, and it does not dispose of substantial portion of relief claimed. A rescission order merely returns parties to their positions before the order being rescinded. (3) The interests of justice test for appealability, while more flexible and context-sensitive, does not displace the Zweni considerations. Where a rescission order enables full ventilation of parties' versions and resolution of real issues, while appeal would unnecessarily delay such resolution, the interests of justice do not favour appealability. (4) An appeal lies against the substantive order of the court, not against the reasoning employed to reach that order.