A substitution of parties under CPR 19.2 is not limited to the situation where an interest or liability has passed from one party to the other. Here the interest in the property to which the dispute related had always vested in the claimant, but it had mistakenly issued proceedings in the name of the original claimant. The Court of Appeal allowed the claimant to stand in the place of the original claimant in the proceedings (London Borough of Hounslow v Cumar).