Adelson v Associated Newspapers Ltd [2007] EWCA Civ 701, [2007] All ER (D) 117 (Jul)
There is no reason in principle why permission should not be given both to substitute a claimant under CPR 19.5 and to add new claims that fall within CPR 17.4(3).
However, it is not permissible to rely upon the new claims in order to assist in demonstrating that the action was brought in the name of the wrong party. It is clear from the language of CPR 19.5(3)(a) that the person who made the mistake has to be the person responsible—directly or through an agent—for the issue of the claim form.
He has to be able to demonstrate that, had the mistake not been made, the new party would have been named in the pleading. The nature of the mistake has to be about the name of the party rather than the identity of the party. The mistake has to be a genuine one, one that is not misleading, one that is not such as to cause reasonable doubt as to the person intending to sue, and it must be just to allow the amendment.