Litigators highlight growing tensions between Competition Appeal Tribunal (CAT) demands for greater simplicity and efficiency in economic evidence and the unprecedented complexity of the questions being litigated, according to a new report by a leading provider of economic and financial consulting and expert testimony, Cornerstone Research.
The report, Quantum mechanics: The evolving role of economic evidence in UK competition disputes, draws on interviews with prominent competition litigators from leading law firms— including CMS, Freshfields, Hausfeld, Herbert Smith Freehills Kramer, Linklaters, Quinn Emanuel, and Slaughter and May—alongside Cornerstone Research economists.
It follows the UK Government’s latest consultation on competition redress reform, which closed on 25 September 2026, and the CAT’s Practice Direction 2/2025, which included page limits on some expert reports.
Recent years have been marked both by a series of high-value cases and growing scrutiny of experts by the Tribunal, which has increasingly focused on proportionality and independence, and has challenged what some tribunal members perceive as overly complex or abstract modelling.
Liam Colley, senior vice president and head of Cornerstone Research’s European competition practice, commented on the findings of the report:
“The CAT has been dealing with complex economic issues since its inception in 2003 and has a huge amount of sophistication and judgement. What has changed since the introduction of the class action regime is not the sophistication required, but the sheer scale of what is now at stake in a single case. Claims that would once have been considered exceptional at £1bn have given way to claims of £14bn—an unprecedented figure.
“It would be a mistake to confuse the Tribunal’s pragmatism with an invitation to shy away from doing the complicated economic analysis. The Tribunal is not asking experts to simplify their analysis— in fact, it is being very demanding about what’s going to pass muster. There aren’t shortcuts that experts can take. They have to apply the tools effectively, grounded in the factual matrix, however complex, and explain all that as clearly as they can.”
What has changed since the introduction of the class action regime is not the sophistication required, but the sheer scale of what is now at stake in a single case. Claims that would once have been considered exceptional at £1bn have given way to claims of £14bn—an unprecedented figure.