"(a) the new party is substituted for a party whose name was given in any claim made in the original action in mistake for the new party's name; or (b) any claim already made in the original action cannot be maintained by or against an existing party unless the new party is joined or substituted as plaintiff or defendant in that action."
“Paragraphs 3 and 4 [of the Particulars of Claim] are not admitted and the status of the Claimants and their entitlement to bring proceedings are for them to prove.”
“[55]CPR 19.5 (3)(a) makes it a precondition of substituting a party on the ground of mistake that: "The new party is to be substituted for a party who was named in the claim form in mistake for a new party" It is clear from this language that the person who has made the mistake must be the person responsible, directly or through an agent, for the issue of the claim form. It is also clear that he must be in a position to demonstrate that, had the mistake not been made, the new party would have been named in the pleading. [56] The nature of the mistake required by the rule is not spelt out. This Court has held that the mistake must be as to the name of the party rather than as to the identity of the party, applying the generous test of this type of mistake laid down in Sardinia Sulcis. The 'working test' suggested in Weston v Gribben, in as much as it extends wider than the Sardinia Sulcis test, should not be relied upon. [57] Almost all the cases involve circumstances in which (i) there was a connection between the party whose name was used in the claim form and the party intending to sue, or intended to be sued and (ii) where the party intended to be sued, or his agent, was aware of the proceedings and of the mistake so that no injustice was caused by the amendment. In SmithKline, however, Keene LJ accepted that the Sardinia Sulcis test could be satisfied where the correct defendant was unaware of the claim until the limitation period had expired. We agree with Keene LJ's comment that, in such a case, the Court will be likely to exercise its discretion against giving permission to make the amendment.”
“[20] Mr Morgan [for the directors, the respondents on the appeal] also submitted that the wider reading of rule 19.5(3)(b) would mean that it would rarely be necessary to resort to rule 17.4 or rule 19.5(3)(a) in a case of mistake. As to that, we do not have to decide the position, but it occurs to me that, if a party sought to use rule 19.5(3)(b) in what was really a case of mistake but in which rule 17.4 or rule 19.5(3)(a) could not for some reason be satisfied, the court, in considering the exercise of its discretion, might well take a dim view of an attempt to escape the limits imposed in the express provisions dealing with mistake cases by resort to this other, arguably more general, provision, even if the court found that the case fell within the language of rule 19.5(3)(b) as a matter of its natural reading. [21] Considering the application to amend in the light of these considerations, I am not persuaded by the distinction which Mr Morgan seeks to draw between a case where the original claimant has a cause of action, even if one to which there is a cast iron defence on the basis of which the claim could be struck out, and another where there is a proper cause of action but the claim is not the right party to bring it because he does not have the necessary locus standi, and the claim could be struck out on that basis. [22] Mr Morgan submitted that to allow a substitution on such a case would permit the possibility of a claim being brought by a complete stranger against the relevant defendant and then, outside the limitation period, that claim being sought to be adopted or validated by the substitution of the relevant company as claimant. [23] Mr Irwin is not, of course, a complete stranger. His task is to collect in the assets of the company for the benefit of it and its creditors, and the claim which he asserted was avowedly brought on the part of the company. For my part, the idea of a complete stranger bringing such a case seems rather fanciful. If for some reason it were to prove real, it seems to me that the court would be likely to regard it as an unsuitable exercise of the court's discretion to substitute the company as claimant outside the limitation period for a complete stranger who had brought a case within the limitation period, which could no doubt have been struck out because he had no right to bring the claim. It seems somewhat unlikely that if this hypothetical complete stranger were to bring proceedings within the limitation period, it would in fact assert the same cause of action as that which the company could itself assert but had chosen not to. [24] It seems to me that the present case is one in which the substitution is necessary for the determination of the original claim because the particular claim cannot be maintained unless the company is substituted as claimant. The original claim is a claim that the respondents were in breach of duty in causing the company to enter into the contract, thereby causing the company loss. The claim, as amended with the substituted claimant, is identical. The original claim cannot be maintained successfully; the new claim can be maintained successfully, subject obviously to proof of the facts. If it is so asserted, it is the identical claim but with a substituted and correct claimant.”
“[41] Where the requirements of section 35(6)(a) of the 1980 Act andCPR r.19.5 (3)(a) are satisfied, the court has a discretion whether or not to allowsubstitution. The existence of this discretion might be thought sufficient to enable anypotential injustice to be avoided, without the need to try to draw distinctions between different categories of mistake.”
“ On the contrary, it seems to me that the court should generally be willing to "excuse such mistakes", in the sense of permitting substitution, even if there is no good explanation, where – as the Master found to be the case here – there is no prejudice to the party who is substituted. The court's discretion should not be exercised in a way that amounts, in effect, to punishing a party for the harmless error of its legal representatives.”