Henry Mostyn

Partner Antitrust & Competition
Kirkland & Ellis International LLP

London +44 20 7469 2238

Henry Mostyn

Practices

Overview

Henry Mostyn is an antitrust and competition partner in the London office of Kirkland & Ellis International LLP.

Henry’s practice focuses on EU and UK competition law, including merger control, anticompetitive agreements and abuse of dominance rules.

Henry has represented clients before the European Commission and the UK Competition and Markets Authority, as well as litigation before the European Courts in Luxembourg and the UK High Court. His particular focus is on the application of the abuse of dominance rules to the technology sector and emerging digital regulation.

Prior to joining Kirkland, Henry was involved in the following matters:

  • Google in various EU, UK, and global matters, including:
    • The EU Commission’s landmark Shopping decision and subsequent appeal to the European General Court in Luxembourg;
    • The EU Commission’s investigation into Android and appeal to the General Court;
    • The UK online map provider Streetmap’s litigation.
  • Google in relation to the EU’s Digital Markets Act and the EU’s first investigations under that Act.
  • Google in relation to the first two investigations under the UK’s new regulatory regime in digital markets.
  • Sony in Microsoft’s proposed acquisition of Activision Blizzard.
  • Disney in various antitrust cases and acquisitions.
  • IBM in various matters.
  • Sun Capital in several acquisitions.
  • Sony Music Entertainment in its acquisition of AWAL and Kobalt Neighbouring Rights businesses from Kobalt Music Group Limited.
  • Sony Corporation of America on the EU antitrust aspects of the $2.2 billion acquisition of EMI Music Publishing.
  • Santander in its joint venture with Credit Agricole.
  • Celanese in a European Commission antitrust investigation.
  • Chemours in a successfully concluded European Commission antitrust investigation.
  • JCB in an antitrust investigation by the Competition Commission of India.
  • DuPont in connection with a European Commission investigation into a collaborative arrangement between DuPont and Honeywell to develop a new automotive refrigerant.
  • Lafarge in its $50 billion merger of equals with Holcim.
  • Walgreens Boots Alliance in the acquisition of its Alliance Health Business by AmerisourceBergen.

Cleary Gottlieb Steen & Hamilton LLP

  • Partner
  • Associate

More

Thought Leadership

Publications

Co-Author, “Generative AI: Practical Considerations for Companies and Boards”, The Review of Securities & Commodities Regulation, 2025

Co-Author, “An Oasis or a Mirage? How Dynamic Pricing Is Assessed Under UK Competition and Consumer Protection Law”, Competition Law Journal, 2024

Co-Author, “The Dominance and Monopolies Review – 11th Edition”, Law Business Research

Co-Author, “European Union, Global Overview and United Kingdom”, Dominance, Getting the Deal Through, 2023

Co-Author, “The Dominance and Monopolies Review – 10th Edition”, Law Business Research

Co-Author, “European Union and Global Overview”, Dominance, Getting the Deal Through, 2022

Editor and Co-Author, “The Dominance and Monopolies Review”, Law Business Research, 2016–2021

Co-Author, “European Union and Global Overview”, Dominance, Getting the Deal Through, 2021

Co-Author “Rigid Justice is Injustice: The EU’s Digital Markets Act Should Include An Express Proportionality Safeguard”, Ondernemingsrecht, 2022

Co-Author “Competition Enforcement: Is the Abuse Toolbox Adequate?”, Research Handbook on the Law and Economics of Competition Enforcement, Edward Elgar Publishing, 2022

Co-Author “‘Compare The Market’ Ruling Sends Clear Signal To CMA”, Law360, 2022

Editor and Co-author “The Dominance and Monopolies Review”, Law Business Research, 2016–2021

Co-Author “European Union and Global Overview”, Dominance, Getting the Deal Through, 2021

Co-Author “Do We Need to Regulate Equal Treatment? The Google Shopping Case and the Implications of its Equal Treatment Principle for New Legislative Initiatives”, Journal of European Competition Law & Practice, 2020

Co-Author “Exploitative Abuses, Price Gouging & COVID-19: The Cases Pursued by EU and National Competition Authorities”, Concurrences – Revue des Droits de la Concurrence, 2020

Co-Author “Reforming EU Merger Control to Capture ‘Killer Acquisitions’ – The Case for Caution”, Competition Law Journal, 2020

Co-Author, “European Union - Access to Online Platforms and Competition Law”, Global Competition Review, 2020

Co-Author, “European Union”, Dominance, Getting the Deal Through, 2020

Co-Author, “Competition in Display Ad Technology: A Retrospective Look at Google/Doubleclick and Google/Admob”, CPI Antitrust Chronicle, 2019

Co-Author, “European Champions – Why Politics Should Stay Out of EU Merger Control”, Concurrences – Revue des Droits de la Concurrence, 2019

Co-Author, “Access to Online Platforms and Competition Law”, E-Commerce Competition Enforcement Guide, 2018

Co-Author, “European Union”, Dominance, Getting the Deal Through, 2018

Co-Author, “The European Union”, The Dominance and Monopolies Review, 2017

Co-Author, “European Union”, Dominance, Getting the Deal Through, 2017

Co-Author, “The European Union”, The Dominance and Monopolies Review, 2016

Co-Author, “The European Union”, The Dominance and Monopolies Review, 2015

Co-Author, “The European Union”, The Dominance and Monopolies Review, 2014

Co-Author, “Internet & Antitrust: An Overview of EU and National Case Law”, e-Competitions

Recognition

Legal 500 UK (2026): Recommended for EU and competition

Legal 500 UK (2026): Recommended for Competition Litigation

Global Competition Review (2024): Listed in GCR 40 Under 40

Credentials

Admissions & Qualifications

  • 2011, Admitted to practice as a Barrister of England and Wales
  • 2019, Bar of Ireland
  • 2026, Brussels (B List)

Education

  • BPP Law School, LondonDiploma in Law2009
  • Pembroke College, University of OxfordB.A., Mathematics2008