Yesim Kul & Ors v DWF Law LLP

An appellate court will rarely permit a party to advance an unpleaded and materially different case after trial. The court must consider the nature of the new point, the need for further evidence, prejudice to the respondent, the explanation for the omission, the merits, and the proper allocation of court resources.

A prospective declaration should not be pursued on appeal where the alleged future risk lacks an evidential foundation. A change of counsel and fresh analysis of the case will not ordinarily provide a good explanation for raising the point late.

The claimants had brought personal-injury claims arising from road traffic accidents. Solicitors acting for insurers used a spreadsheet containing the claimants’ names and medical information in other litigation to support allegations of fundamental dishonesty. The spreadsheet was later pseudonymised for use in the relevant claims.

The claimants brought proceedings under the Data Protection Act 2018 seeking declarations and compliance orders concerning past processing. Eady J dismissed the claims: [2025] EWHC 1824 (KB).

On appeal, the claimants ultimately sought declarations governing a supposed future risk of non-pseudonymised processing. The central question was whether the Court of Appeal should allow that new and unpleaded case to be advanced after trial.

1. Appeal dismissed. Warby LJ, with whom Asplin and Newey LJJ agreed, refused to entertain the claimants’ new case. It had not been pleaded, was outside the grounds and permission to appeal, and differed fundamentally from the historical-processing claim tried below.

2. A substantive alteration of an appellant’s case requires permission to amend. The court applied the established caution concerning new points on appeal. The proposed case would require a fresh factual evaluation of future risk, would have altered the conduct of the trial, and had been advanced without a cogent explanation or formulated amendments. The prejudice to DWF and the interests of justice outweighed its limited merits.

3. The merits did not justify allowing the change. Cooper v National Crime Agency [2019] EWCA Civ 16 remained binding authority for the reasonable-necessity approach applied by the judge. The court saw no relevant inconsistency with the proportionality authorities relied on by the claimants, and no realistic prospect that their new legal argument would alter the result.

4. Most importantly, there was no tenable evidential basis for alleging a future risk that DWF would use the non-pseudonymised spreadsheet. The March 2023 order was intended to resolve pseudonymisation across the relevant claims, and DWF confirmed that only the pseudonymised version had since been relied on. If a genuine concern had existed, it should first have been raised in correspondence and, if necessary, in the County Court proceedings.

5. Independently, the court held that relief from sanctions would be refused. The default was serious and significant, no good reason had been given, and the overall circumstances decisively favoured refusal.

• Court of Appeal (Civil Division): Appeal dismissed: [2026] EWCA Civ 1130 .
• High Court of Justice, King’s Bench Division, Media and Communications List: Eady J dismissed the data-protection claims: [2025] EWHC 1824 (KB) .