JSC Commercial Bank “PrivatBank” v Igor Valeryevich Kolomoisky & Ors

Permission to amend a defence is a broad case-management discretion governed by the overriding objective. The court considers the timing and history of the amendment, its clarity and particularity, and the prejudice to each side. An amendment must disclose a case with a real prospect of success. It must be realistic, coherent and properly particularised, and supported by evidence establishing a sufficiently arguable case. Where expert evidence can support the proposed legal argument, the court should not resolve competing interpretations at the amendment stage. If the issue remains properly arguable, its correctness should ordinarily be determined at trial after the evidence has been tested.

The claimant brought an unjust enrichment claim against the defendants. The Third to Eighth Defendants applied under CPR 17.1(2) to amend their defence. The proposed amendments concerned whether the property received matched the claimant’s loss and whether any restitutionary liability should be capped by the value of the claimant’s loss.

The claimant opposed those amendments on the grounds that they were late, unsupported by the existing expert evidence and raised a new argument. The application was determined on the papers. The central issue was whether the proposed case was sufficiently arguable and whether the procedural factors justified permission to amend.

1. Application granted. The court permitted the Third to Eighth Defendants to amend their defence in the form sought, subject to the parties agreeing and submitting an order for approval.
2. Under CPR 17.3, the court has a broad discretion to permit amendments. That discretion must be exercised in accordance with the overriding objective and the duty under CPR 1.2(a). Relevant factors include the timing and history of the amendments, whether they could have been advanced earlier, their clarity and particularity, and the prejudice to the opposing and amending parties.
3. The merits threshold is whether the amendment has a real prospect of success. Applying Swain v Hillman [2001] 1 All ER 91, this means more than a merely arguable case: the case must carry some degree of conviction and be realistic rather than fanciful. The pleading must also be coherent and properly particularised. Permission should be refused where the proposed case lacks evidential support, applying Kawasaki Kisen Kaisha Ltd v James Kemball Ltd [2021] EWCA Civ 33.
4. The proposed mismatch and loss-cap arguments were a further development of the existing defence and did not create prejudice requiring refusal. The amendments raised a new issue, but the claimant was already required to address related factual matters at trial.
5. The expert evidence on Ukrainian, Cypriot and English law was capable of supporting the amendments with sufficient conviction. Whether that evidence ultimately established the pleaded propositions was a matter for trial. The court declined to resolve the unsettled question whether English unjust enrichment law limits recovery by reference to the claimant’s loss, notwithstanding the authorities cited on that issue.