Speaking in London this morning (4 December) at the Seventh Annual UK Competition Litigation Conference, Ben Tidswell, Chair of the Competition Appeal Tribunal (CAT), delivered what felt less like an after-dinner speech and more like a sharp course-correction for the competition litigation community.
Against the backdrop of the CAT’s new Practice Direction 3/2025: Expert Evidence, published on 2 December 2025, Tidswell used his keynote to issue a stern warning to both lawyers and economists: expert evidence is drifting into advocacy and excess, and the Tribunal is now prepared to pull it firmly back on track.
With a nod to the well-worn truth that competition law is a “messy mix of law and economics”, he urged practitioners to rethink how that mix is handled in practice – and did so with enough dry humour to keep his audience of what he later described as a “cartel of misbehaviour” listening very closely.
Two core messages: impartiality & excess
Tidswell warned that the independence and impartiality of expert evidence are slipping, as economists become increasingly entangled in the broader litigation strategies of the parties instructing them.
Too often, he suggested, expert conclusions appear to “track the client’s interests” with unnerving precision, leaving little room for alternative plausible outcomes or any acknowledgement of the inherent limits of the analysis.
When the Tribunal detects even a hint of advocacy or partiality in one material respect, it inevitably casts doubt over the integrity of the entire report, he said.
The CAT Chair reserved equally sharp criticism for the sheer volume and complexity of economic evidence now routinely submitted. Reports stretching into the thousands of pages, layered with repeated summaries and attempts to pre-empt every possible argument, no longer assist the Tribunal—they overwhelm it.
Rather than clarifying the issues in dispute, this sprawling material often obscures them, he said, adding that for a Tribunal operating under significant time pressure, even with panels steeped in economic expertise, such deluges of documentation are impossible to digest in any meaningful way.
The ideal expert, he reminded the room, is straightforward in concept but elusive in practice: independent, considered and succinct, clearly setting out the key points of difference between experts.
Practice Direction 3/2025: the formal reset
Tidswell was explicit that the new experts’ Practice Direction represents a reset in expectations. He stressed that this is not about blaming individuals, but about “recognising that current practices are no longer working”, and that the Tribunal is now signalling a firmer, more interventionist approach.
The Practice Direction, he said,
“signals a reset in the Tribunal’s expectations about the preparation of expert evidence”
and a
“consistently reduced tolerance of advocacy and excessive volume.”
Limiting lawyers’ fingerprints
One provision appeared particularly controversial to the audience: paragraph 25 of the Practice Direction, which significantly curtails the role of legal teams in drafting expert reports and joint statements.
During the Q&A, one delegate put what many were thinking: is this a “radical departure”, and what does it actually mean for day-to-day conversations between lawyers and experts?
Tidswell acknowledged that this is “the point that’s generated the most internal debate” within the Tribunal. He resisted calls for more detailed, prescriptive rules, on the basis that some dialogue between experts and lawyers is both inevitable and necessary—but the balance has shifted too far.
His message was clear: the Tribunal will not police every interaction, but expects practitioners to exercise judgment, and will look critically at evidence where that judgment appears to have failed.
Joint statements and isolation of experts
Tidswell was particularly concerned about what happens behind the scenes of joint expert statements. The Tribunal has seen signs that joint work is being massaged by the wider litigation teams, leading to artificially narrow areas of agreement and entrenched positions that bear the hallmarks of client strategy rather than professional consensus.
Under the new directions, joint expert work will come under far closer Tribunal supervision. Joint meetings are now expected to take place without lawyers present, and joint statements must be drafted by the experts themselves—an attempt to eliminate behind-the-scenes shaping of consensus.
Culture change, not box-ticking
Throughout, Tidswell emphasised that the Practice Direction is not a standalone compliance exercise, but part of a broader “change of culture” around expert evidence in the CAT.
Experts must live up to their declarations of independence, rather than treating them as boilerplate. Lawyers must re-calibrate their involvement, resisting the temptation to treat experts as quasi-advocates or as vehicles to advance every conceivable theory, he said.
Both communities must accept that less can be more: clarity, balance and proportionate analysis will carry greater weight than sprawling, client-friendly models, he stressed.
The message was firm, but not hostile. The Tribunal recognised it has, over time, acquiesced in practices that are no longer working, and is now signalling, politely but unmistakably, that the line has moved.
The conference was the Seventh Annual UK Competition Litigation Conference organised by Monckton Chambers and NERA.
By Sylwester Frazzoni in London
