Jack is ranked as a “leading junior” in Competition Law in the 2024 Chambers & Partners and Legal 500 publications (having been recognized as a “rising star: tier 1” and “up and coming” in the 2022 and 2023 editions). He was nominated for the 2024 Legal 500’s Competition Law Junior Barrister of the year. Jack’s clients include, for example, Google in multiple matters; Meta; Intel; Samsung; the CMA; and numerous class representatives and respondents in collective proceedings. He has advised on an extensive array of competition law matters and represents clients in many of the leading cases, including those regularly featured in The Lawyer’s “Top 20 cases” of the year.

Cases

Abuse of dominance

• C-240/22 P and T-286/09 RENV Intel Corporation v Commission: acted for Intel in securing annulment of a €1 billion fine in the General Court following Intel’s successful appeal to the CJEU concerning alleged infringements of Article 102 (abuse of dominance). Jack now acts for Intel in seeking €600 million in default interest arising from the annulment (Case T-236/22). See here, here and here.
• T-334/19 Google v Commission: Jack represented Google in its successful appeal against the European Commission’s Decision imposing a €1.5 billion fine in relation to Google’s search and advertising services (AdSense). Jack conducted the oral advocacy in relation to two out of three of the alleged abuses. See here and here.
• 1378/5/7/20 Epic Games v Google: instructed by Google in relation to Epic’s claims regarding the Google Play Store. The Lawyer ranked this as one of the top 20 cases for 2023: see here.
• 1589/5/7/23 Foundem v Google: instructed by Google in relation to Foundem’s claims regarding Google search results and rankings.
• 1424/5/7/21 Kelkoo v Google: instructed by Google in relation to Kelkoo’s claims regarding Google search results and rankings and Google AdSense.
• 1379/5/7/20 Kerilee Investments v International Tin Association (ITA): instructed by the ITA in relation to Kerilee’s claims concerning alleged membership restrictions and subsidies.
• Intas Pharmaceuticals & Others v Competition and Markets Authority [2023] CAT 56: instructed by Intas, Accord Healthcare and Accord-UK in an appeal in respect of the CMA’s Hydrocortisone Decision finding excessive pricing.

Collective proceedings

• Dorothy Gibson v Pride Mobility Products Ltd [2017] CAT 9: Jack was junior counsel for the respondent in the first “opt-out” class action competition proceedings brought under the new UK private damages regime introduced by the Consumer Rights Act 2015. See here and here.
• Le Patourel v BT Group PLC [2021] CAT 30, [2021] CAT 32, [2022] EWCA Civ 593 and [2024] CAT 76: Jack was instructed by the class representative in the opt-out collective proceedings to reach trial in a claim against BT for alleged excessive pricing in abuse of its dominance position in standalone landline telephone services. More information available here and here. The Lawyer ranked this as one of the top 20 cases for 2024: see here.
• 1408/7/7/21 and 1673/7/7/24 Coll v Google and Roger v Google: instructed by Google in relation to claims (included alleged excessive pricing, bundling, and restrictive practices) regarding the Google Play Store.
• Spottiswoode v Nexans, NKT and Prysmian [2024] CAT 31: instructed by Prysmian in relation to follow-on proceedings relying on a decision of the European Commission dated in Case COMP/39610 concerning agreements in respect of the (extra) high voltage underground and submarine power cables sectors.
• 1630/7/7/23 Roberts v Northumbrian Water: instructed by Northumbrian Water in relation to standalone collective proceedings concerned alleges breaches of a dominant position in providing misleading information to regulatory bodies and alleged higher prices for sewerage services.
• 1266/7/7/16 Merricks v Mastercard: instructed by the class representative (and the over 40 million consumers represented) in respect of the extent to which unlawfully-inflated merchant service charges (MSCs) were passed-on by retailers to consumer class members. At trial, Jack cross-examined each of the four expert economists.
• 1689/7/7/24 Which? v Apple: instructed by Which?, the proposed class representative, in proposed opt-out collective proceedings concerning iCloud.

Anti-competitive agreements

• Granville Technology (and others) v Samsung (and others) – acted for Samsung in these domestic follow-on proceedings regarding a cartel found in Decision in CASE AT.39437 – TV and computer monitor tubes.
• The FCA: instructed by the FCA in relation to its first decision under its competition enforcement powers. More information is available here.

Consumer

• Viagogo AG v Competition and Markets Authority [2019] EWHC 1706 (Ch): instructed by the CMA in relation to its secondary ticket market enforcement action against viagogo, including matters relating to service out of jurisdiction and alternative method of service. More information is available here.
• The CMA: instructed by the CMA in relation to its leasehold investigation and enforcement proceedings. More information is available here.

Jurisdiction challenges

• Vauxhall Motors Ltd & Others v Denso Automotive UK Ltd & Others [2025] EWHC 213 (Ch): successfully represented Denso in respect of its jurisdictional applications to set aside service out and decline any jurisdiction in any event on the basis of forum non conveniens. See here.

Section 179 of the Enterprise Act 2002 reviews

• Motorola v CMA [2023] CAT 76: acted for the Home Office (intervening) in relation to Motorola’s application for a review of the CMA’s decision in its Final Report on “Mobile radio network services” dated 5 April 2023. See here.

EU Law

Having been called to the Bars of Ireland and Northern Ireland, Jack retains his rights of privilege to advise clients confidentially on matters of EU law and to represent clients before the EU Courts. He has been instructed in a number matters before the General Court and Court of Justice:

• T-745/20: Symphony Environmental Ltd v European Commission, Council and Parliament: non-contractual liability.
• C-240/22 P and T-286/09 RENV Intel Corporation v Commission: acted for Intel in securing annulment of a €1 billion fine in the General Court following Intel’s successful appeal to the CJEU concerning alleged infringements of Article 102 (abuse of dominance). Jack also acted for Intel in its €600 million in default interest claim arising from the annulment (Case T-236/22), which subsequently settled. See here and here.
• T-334/19 Google v Commission: instructed by Google in relation to Google’s appeal against the European Commission’s Decision concerning Google’s search and advertising services (Adsense). Jack conducted the oral advocacy in relation to two out of three of the alleged abuses. See here.

During a traineeship at the Court of Justice with Judge Vajda (the last UK Judge)prior to coming to the Bar, Jack worked on cases including: Kadi II (the effect of European procedural rights), Pringle (the validity of the European Stability Mechanism), Abdulrahim (continuing interest to bring an action for annulment), and Inuit I (the definition of regulatory acts in Article 263 TFEU for the purposes of standing).

UK-EU Relations Law

As the legal directories say, Jack is “one of the leading voices of Brexit law in the UK”. He has been at the forefront of all matters in connection with Brexit and the UK’s new relationship with the EU post Brexit, UK-EU Relations Law. Jack has given evidence to Parliament on the topic, and his publications have been cited by the High Court ([2022] EWHC 929) and the Supreme Court ([2024] UKSC 24).

Jack is the founder and editor of https://eurelationslaw.com. He has published extensively on the topic (see publications below). He is also the co-editor of a book on the constitutional implications of the Miller (Article 50) case (with Professor Mark Elliott and Professor Alison Young): available here.

He has been instructed in a range of Brexit litigation, including Miller 1 (Article 50 litigation), Eurotunnel v Secretary of State (Brexit no deal ferry contracts), and Heathrow v Treasury (decision to remove tax reliefs at the end of the Brexit transition period).

He has advised both public and private clients on a range of constitutional matters arising out of Brexit and EU Relations Law, including in relation to: the Article 50 process, the EU Withdrawal Acts, the use of the royal prerogative, acquired EU rights, the transition period, the Withdrawal Agreement and the Trade and Cooperation Agreement. Jack has spoken about these, and related, topics at numerous events and given oral evidence to Parliament. See here.

He also undertook a six-month secondment in the Bank of England’s Legal Directorate’s EU Withdrawal Unit.

Cases

Jack was ranked as “Rising Star: tier 1” for Procurement Law in the 2022 Legal 500. He has been instructed on both claimant and defendant sides in major procurement litigation.

Jack also has experience of mediation in procurement dispute contexts, and has oral advocacy experience in the TCC. He has frequently advised on the formation of confidentiality rings and various interlocutory matters.

Cases

• Bombardier Transportation Ltd v Merseytravel – Jack was instructed by the defendant to defend a damages claim in relation to contracts for the design, build and maintenance of rolling stock and the modernisation of maintenance depots.
• CAF v High Speed 2 [2018] EWHC 311 (TCC) – Jack was instructed by the claimant to challenge the pre-qualification stage of the procurement for the provision of rolling stock and associated services for the new high-speed railway known as HS2.
• Marston v Ministry of Justice [2018] EWHC 3168 (TCC) – Jack was instructed by the defendant in response to a claim against an award decision in respect of contracts for the delivery of approved enforcement agency services.
• Serco v Ministry of Defence – Jack was instructed by the defendant in response procurement challenge relating to defence fire and rescue project.
• Eurotunnel v Secretary of State for Transport [2019] EWHC 419 (TCC) – Jack was instructed by Eurotunnel in relation to its (expedited) procurement and state aid law challenges to the award of Brexit ferry contracts. More information is available here.
• Medequip v Staffordshire County Council and Wiltshire County Council – Jack was instructed by Medequip in relation to its claims against two authorities concerning manifest errors of assessment and abnormally low tender allegations.
• Arriva Rail East Midlands Ltd v Secretary of State for Transport [2019] EWHC 2047 (TCC), [2019] EWHC 2922 (TCC) and [2019] EWCA Civ 2259 – Jack was instructed by the claimant in respect of its procurement challenge in relation to the operation of the East Midlands Franchise. This included representing Arriva before the Court of Appeal: more information is available here.
• MMG v HMRC – Jack was instructed by the defendant. The case settled following a mediation.

Before becoming a Barrister, Jack was a College Lecturer at Brasenose College (University of Oxford) where he taught Administrative Law and Constitutional Law. Due to this academic and teaching background, Jack has experience and expertise beyond his date of Call in a range of public law matters.

Cases

• R (Miller and Dos Santos) v Secretary of State for Exiting the European Union [2017] UKSC 5 – junior counsel for one of the Interested Parties (Pigney and others: “The People’s Challenge”) in the Article 50 Brexit litigation at both Divisional Court and Supreme Court levels. The case concerned whether Parliamentary involvement was necessary to trigger any UK withdrawal from the EU or if mere use of executive power (under any subsisting prerogative power) was sufficient. More information is available here.
• AI and XH v Secretary of State for the Home Department [2016] EWHC 1898 (Admin) – junior counsel for one of the Claimants (AI) at the Divisional Court level in his judicial review concerning whether the royal prerogative to withdraw a British Citizen’s passport had been abrogated by the Terrorism Prevention and Investigation Measures Act 2011 or was lawfully exercised in any event.
• BAT Industries Plc (and others) v HMRC [2017] UKFTT 558 (TC) – Jack was junior counsel for HMRC, successfully defending a challenge under EU, ECHR and domestic common law to the provisions of Part 8C (“the restitution interest provisions”) of the Corporation Tax Act 2010 before the First-tier Tribunal. More information is available here. Jack is instructed by HMRC in BAT’s appeal to the Upper Tribunal.
• Heathrow (and others) v HM Treasury and HMRC [2021] EWCA Civ 783 – Jack acted for the claimants challenging the defendants’ removal of tax reliefs at the end of the Brexit transition period and its application of WTO law. See here.

The great majority of Jack’s work includes a commercial element. In particular, Jack’s Competition Law, Procurement Law and Sports Law practices involve a considerable amount of commercial and contractual analysis.

Jack has oral advocacy experience before the County Court, the First Tier Tax Tribunal, the Competition Appeal Tribunal, the High Court, and the General Court in Luxembourg. He has represented clients at CMCs, PTRs and trials. He has also sat as an Arbitrator, appointed by Ofwat, in a dispute under the Water Industry Act 1991, and has advised on the Arbitration Act 1996.

Jack has advised and assisted on a range of sports matters, particularly in a football context. He has advised and represented national sports governing bodies, clubs and private individuals in relation to:

• agent fees
• arbitration proceedings (particularly Rule K arbitrations)
• British Rowing disciplinary proceedings
• contractual disputes
• employment rights
• FA disciplinary proceedings
• fraud and unlawful means conspiracy allegations
• intermediary activities
• mitigation
• player transfers
• representation agreements (including with minors)
• safeguarding matters
• settlement agreements
• sponsorship agreements
• stay applications
• strike out applications

Cases

Competition

Leading Junior: “He works collaboratively, is intelligent and responsive. Jack has a good manner with clients and has the ability to easily break down complex and difficult concepts.” “Jack brings tremendous energy to the counsel team and is a pleasure to work with.” – Chambers UK and Chambers Global, 2025

Leading Junior: “A first class junior – really takes ownership of the case and gives it his all. Powerful strategic judgement.” – Legal 500, 2025

Leading Junior: “He navigates what are often highly complex and technical issues with great ease.” “He is tenacious and has tremendous energy.” “Jack is an impressive operator in the field of competition litigation, including collective proceedings.” “He is a pleasure to work with.” “Jack is an attentive, thoughtful, and user-friendly junior counsel.” – Chambers UK, 2024

Leading Junior: “Very hard working and approachable, Jack adopts a sensible approach to cases. He has a calm, well-structured and unflappable style of advocacy; he is able to deal with heavyweight cases and more senior barristers without any problems at all.” – Legal 500, 2024

Up and Coming: “selected to represent an enviable line-up of clients ranging from the CMA to global technology companies”; “notable experience of CMA appeals, and damages claims, including collective actions”; and  “A very impressive junior: he’s tenacious and has strong analytical skills, and is a strong team member.” – Chambers UK and Chambers Global, 2023

Rising Star: “Highly intelligent and articulate, Jack is able to get to grips with complex issues and deal with a high volume of work; no doubt a future silk in the making.” – Legal 500, 2023

Up and Coming: “He rolls up his sleeves and gets stuck into the detail.” “He is super eager, razor sharp and great to work with.” “selected to represent an enviable line-up of clients” – Chambers UK and Chambers Global, 2022

Rising Star: “Clever, calm, effective – a team player.” – Legal 500, 2022

EU law and UK-EU relations law

Leading Junior: “Jack Williams is one of the leading voices of Brexit law in the UK.” – Chambers UK, 2025

Leading Junior: “A master of the detail and subject matter. Extremely hard working and good on his feet.” – Legal 500, 2025

Up and Coming: “He knows all the intricacies of the changes since Brexit and he has made it comprehensible. He is a go-to person.” “Jack is a master of detail.” – Chambers UK, 2024

Leading Junior in European law – Legal 500, 2024

Up and Coming: “Jack Williams has acted in a number of momentous cases before the EU courts and has advised various public bodies on the implications of Brexit. Williams has established himself as a particular authority on the emerging area of EU relations law”. “He is enthusiastic, kind and extremely diligent. He is very thoughtful and good to work with.” – Chambers UK, 2023

Procurement law

Rising Star in Public Procurement – Legal 500, 2023

Rising Star: “He is a very enthusiastic junior barrister with excellent drafting skills and real desire to do his very best for the client and the case. He is a pleasure to lead and he has a great career ahead of him.” – Legal 500, 2022

Rising Star: ‘He is a very enthusiastic junior barrister with excellent drafting skills and real desire to do his very best for the client and the case. He is a pleasure to lead and he has a great career ahead of him.’ – Legal 500, 2021

• Dover Grammar School for Boys, 2002 – 2009
• First Class Degree in Law – University of Cambridge, 2012
• Distinction in the BCL (Masters in Law) – University of Oxford, 2014
• Outstanding in the BPTC – BPP University, 2015

Awards and prizes

Bar Professional Training Course: BPP & Gray’s Inn

• Arden Scholarship (Gray’s Inn), 2015
• Bedingfield Scholarship (Gray’s Inn), 2014
• Residential Scholarship (Gray’s Inn), 2014
• Excellence Award (BPP), 2014

Postgraduate: Oxford University

• Vinerian Proxime Accessit Scholarship, 2014 (for coming overall 2nd in the year)
• The University’s Prize for Comparative Public Law, 2014 (for coming top in the year)

Undergraduate: Cambridge University

• The University’s ‘Littleton Chambers Prize for Labour Law’, 2012 (for coming top in the year)
• The University’s ‘E.C.S Wade Prize for Administrative Law’, 2011 (for coming top in the year)
• Ms Payne (1610) Scholarship, 2012
• The College’s ‘Adderley Prize for Law’, 2012
• The College’s ‘Lauterpacht Prize for International Law’, 2011
• The College’s ‘Simmons and Simmons Prize for Constitutional Law’, 2010
• Gooderson Memorial Scholarship, 2013