Natalie Todd and Anastasia Tropsha analyse a recent decision where the court rejected the substitution of a law firm as the claimant following the assignment to it of the claim. The agreement, entered into by way of an innovative litigation finance arrangement, was not one of the two models permitted by the CLSA 1990 and therefore invalid. This article was first published on Lexis®PSL on 30 July 2021 and can be viewed here.