1. By a generally endorsed writ issued in 2011, Greater Beijing Region Expressways Limited (“GBRE”) claimed damages against the appellants for professional negligence. 2. In 2012, GBRE purported to assign its causes of action against the appellants (the “Assignment”) to Beijing Tong Gang Da Sheng Trade Co., Ltd (“Beijing Tong Gang”). The writ, which had not been served, was then amended such that Beijing Tong Gang became the plaintiff (the “Plaintiff”) in place of GBRE which ceased to be a party. 3. In 2013, the appellants sought to strike out the Plaintiff’s claim on the ground that the Assignment was champertous and void (“the strike out application”). In response, the Plaintiff sought to add GBRE as a plaintiff (“the joinder application”) as GBRE would have been met with a successful limitation defence were it to issue a new writ by that time. 4. Before the lower courts, the appellants were successful in the strike out application. However, the Court of Appeal allowed the joinder application on the basis that no issue of limitation arose since it did not involve a new cause of action. 5. The issues on appeal are as follows: (1) whether the joinder application is caught by limitation (“Issue of Limitation”); and (2) if so, whether leave should be granted under Order 20 rule 5(3) of The Rules of the High Court, Cap 4A to permit joinder (“Issue of Mistake”). Issue of Limitation 6. The Court held that an application to add or substitute a party would result in a ‘new claim’ as defined in section 35(2) of the Limitation Ordinance, Cap 347 (“LO”). If the application is made after the expiration of the limitation period current at the time of the commencement of the action, it must come within rules of court as required under section 35(3) and (5) of LO. 7. The Court of Appeal was thus wrong to conclude that because no new cause of action was involved in the joinder application, the limitation provisions of section 35 of LO did not apply. 8. The fact that GBRE was once a party does not make any difference, as it had ceased to be a party altogether as a result of the amendment in 2012. GBRE was as much a new party as if the original writ was issued in the Plaintiff’s name after the impugned Assignment, and the issue of limitation arose on the joinder application. Issue of Mistake 9. As for the Respondent’s alternative submission on a genuine mistake under Order 20 rule 5(3), the authorities clearly show that the mistake has to be a mistake as to the name rather than the identity of the party or as to legal rights. 10. There was no mistake in the relevant sense here, as the Plaintiff wished to sue as the assignee, sued as such and was correctly named. The mistake was in the belief that the Assignment was valid and effective, and Order 20 rule 5(3) does not apply. CONCURRING JUDGMENT OF LORD HOFFMANN NPJ: 11. Lord Hoffmann NPJ took the view that a case within Order 15 rule 7, where a new party succeeds to the interest of an existing party, falls outside section 35 of LO. Whether this is because, as a matter of construction of section 35 of LO, it falls outside the definition of a new claim or whether it is a sanctioned exception, does not seem to matter. 12. Either way, the power of the court under Order 15 rule 7 can be exercised whether the limitation period has expired or not. However, Lord Hoffmann NPJ observed that this does not extend to the substitution of a new party outside Order 15 rule 7, which is the case in the present action.