K Element & Ors v Tesco Stores Limited

Permission for expert evidence under Employment Tribunal (Equal Value) Rules of Procedure 2024 r 10(1) requires the tribunal first to identify the issues in the case. It must then identify the proposed expert’s field and explain how the evidence is necessary, or reasonably required, to resolve those issues.

Permission cannot properly be granted by reference to evolving submissions, provisional market definitions, or open-ended hypothetical questions which are not anchored to the pleaded case. Where the issues and parameters are unclear, the tribunal cannot conduct the required assessment or manage the evidence consistently with the overriding objective.

In extensive equal-pay litigation, store-based claimants alleged that their work was of equal value to that of predominantly male distribution-centre comparators. Tesco relied on material-factor defences based, among other matters, on labour-market rates and the consequences of increasing store pay.

The Employment Tribunal initially refused Tesco permission to call an economist. That decision was remitted following [2025] EAT 26. On reconsideration, the tribunal permitted expert evidence on market rates, competition and hypothetical reactions of competitors, customers, investors and creditors. It later framed questions for the experts.

The claimants appealed the second and third expert-evidence decisions. The central issue was whether permission had been granted without identifying the pleaded issues and the expert evidence reasonably required to resolve them.

1. Appeal allowed. The second and third Employment Tribunal decisions granting permission for economic expert evidence were wrong and fell outside the tribunal’s broad case-management discretion.

2. Rule 10(1) of the Employment Tribunal (Equal Value) Rules of Procedure 2024 restricts expert evidence to that reasonably required to resolve the proceedings. Applying British Airways Plc v Spencer & Ors, the tribunal must assess each identified issue: whether expert evidence is necessary; if not, whether it would assist; and, if so, whether it is reasonably required in the proceedings as a whole.

3. That exercise could not be performed here. The tribunal had not identified the pleaded issues to which the proposed evidence related. It relied instead on formulations in Tesco’s EAT skeleton argument which had evolved beyond both the original application and, in material respects, the pleaded material-factor-defence case.

4. The permitted questions were also insufficiently defined. The labour-market definitions remained provisional; terms such as “competitive” and “market power” were not adequately identified or understood; and the consequences questions left the relevant hypothetical scenarios and assumptions open-ended. The field of expertise was described only as economics, which was too broad.

5. The decision did not establish that economic evidence could never be reasonably required. The parties must first agree, or obtain a determination of, the manageable material-factor-defence issues, the population to which the hearing applies, and the parameters of any expert evidence. Disposal was reserved for written submissions.

• Employment Appeal Tribunal: In Tesco Stores Limited v Ms K Element & Ors [2025] EAT 26, the EAT allowed Tesco’s appeal against the initial refusal of expert evidence and remitted the application to the same Employment Tribunal.
• Employment Tribunal: On 21 March 2025, the tribunal granted permission in principle for economic expert evidence on markets and consequences. On 27 March 2025, it settled questions for the experts.
• Employment Appeal Tribunal: The present appeal allowed the claimants’ challenge to those second and third decisions.