Manifest error in expert determinations: Court of Appeal reaffirms high bar in WH Holding v London Stadium

Overturning a judgment of the Commercial Court, the Court of Appeal in WH Holding Ltd v London Stadium LLP (formerly E20 Stadium LLP) [2026] EWCA Civ 153 rejected a claim to set aside a contractually appointed expert’s determination, even where the Court may have ultimately disagreed with the expert's interpretation of the contract. The decision reiterates the high bar for challenging expert determinations on the grounds of "manifest error".

Background

The dispute arose under a long‑term concession agreement pursuant to which E20 Stadium LLP (now London Stadium LLP) (E20) granted the owner of West Ham United Football Club Limited, WH Holding Limited (WHH), the right to hold football matches at the London Stadium.

The concession agreement contained an “overage” provision, that entitled E20 to share in the gains on certain “Qualifying Transactions” in relation to WHH shares, if the consideration exceeded £125 million.

On 11 November 2021, several WHH shareholders entered into a structured deal with 1890 Holdings, a Czech sports investment platform, comprising of:

• a purchase of existing shares at an agreed price (the Share Purchase);
• a call option over further shares (with both an option premium and a strike price) (the Call Option); and
• a subscription for new shares.

It was common ground that the Share Purchase, taken alone, triggered a payment of approximately £2.5 million under the overage provision. The dispute concerned the Call Option: WHH said it was a separate Qualifying Transaction that did not itself cross the £125 million threshold; E20 said the Share Purchase and Call Option formed a single Qualifying Transaction, so that the Call Option premium fed into the overage formula such that a further £3.6 million was due.

Under the concession agreement, the dispute was to be resolved by expert determination that was to be "final and binding” in the absence of “manifest error”.  The appointed expert accepted E20’s interpretation and determined that the further payment of £3.6 million was due.

WHH challenged the determination on the basis of “manifest error”. The Commercial Court agreed and set it aside. E20 appealed.

The Court of Appeal’s decision

In overturning the Commercial Court's decision, the Court of Appeal reaffirmed the following principles:

• manifest errors are “oversights and blunders so obvious and obviously capable of affecting the determination as to admit of no difference of opinion”[1] (i.e. there is no room for debate) and must be "easily demonstrable without extensive investigation”;[2]  and
• “[a]rguable error will not suffice, however well founded the allegation of error may ultimately prove to be”.[3]

The Court of Appeal distilled this into a single test. Absent specific contractual wording providing otherwise, an error is manifest only if, after investigation limited in time and scope, it is so obvious (and so obviously capable of affecting the determination) that it admits of no difference of opinion.

The Court of Appeal rejected the parties' attempts to further refine or qualify this test – holding that:

• the requirement for "limited investigation" did not equate to "without the need for adversarial argument";

• there is no authority for restricting the reasoning that must be applied to determine a manifest error – in particular, that would prevent a judge from first determining (i) whether there was a mistake, and (ii) whether that mistake was manifest; and

• no special considerations apply in cases involving the application of a contractual formula.

The Court of Appeal disagreed with the Commercial Court’s characterisation of the overage provisions as “admirably clear” and their application as merely a case of “doing the mathematics”.[4] On the contrary, it considered it “perfectly sensible” to treat the structured deal as a single Qualifying Transaction, and noted that the contractual definition was wide enough to admit that reading.

The Court of Appeal emphasised that it was not deciding which interpretation was correct as a matter of pure construction. While it considered that WHH’s alternative construction had real force (and might well be preferred if the Court of Appeal was determining the agreement's proper interpretation) the expert’s reading was not so obviously wrong as to admit of no difference of opinion. Therefore, there was no manifest error and the expert's determination stood.

Practical takeaways

For clients and practitioners, WH Holding v London Stadium offers a number of clear takeaways:

1. The bar for establishing 'manifest error' remains high. The courts will not overturn an expert's decision just because there is a strongly arguable case that the expert misinterpreted the contract. Parties should be realistic when assessing the alleged error given the limited scope for challenging the expert's verdict.
2. There is no scope to alter the legal test for 'manifest error'. The test has been firmly established. In the absence of specific contractual wording, the courts are unlikely to admit further glosses or distinctions for individual cases.
3. Contracts containing expert determination clauses should be drafted carefully. Complex transactions require clear drafting and alternative interpretations should be considered at an early stage. If parties have a particular interpretation in mind, a belt and braces approach may be preferred.