Cleary Gottlieb Steen & Hamilton (London)

Henry Mostyn

Cleary Gottlieb Steen & Hamilton (London)

Henry Mostyn is a partner based in the London office of Cleary Gottlieb Steen & Hamilton. His practice focuses on EU and UK competition law, including merger control, anticompetitive agreements, and abuse of dominance rules. He 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. Mr. Mostyn joined the firm in 2012. In 2011, he completed pupillage at 4 New Square Chambers, Lincoln’s Inn. As an undergraduate he read Mathematics at Pembroke College, Oxford. During 2017, Henry worked at the UK Competition and Markets Authority in the mergers team. He completed the Graduate Diploma in Law at BPP Law School, where he achieved a Commendation. Mr. Mostyn is a member of the Bar in England and Wales. His native language is English.


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Cleary Gottlieb Steen & Hamilton (Cologne)
Cleary Gottlieb Steen & Hamilton (London)
Cleary Gottlieb Steen & Hamilton (Hong Kong)
Cleary Gottlieb Steen & Hamilton (Brussels)
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12032 Bulletin

Nicholas Levy, Henry Mostyn, Paul Stuart, Patrick Todd The EU General Court partially annuls the Commission’s decision against a Big Tech company for non-price based abuses of dominance (Google Android)


In September 2022, the General Court partially annulled the European Commission’s 2018 Google Android decision, which fined Google €4.3 billion for abuses of dominance relating to apps it offers for its Android mobile operating system (“OS”). The Court also found that the Commission’s (...)

Henry Mostyn, Jonas Zenger The UK Competition Appeal Tribunal agrees with the appellant that a fine imposed for anticompetitive MFC clauses should be set aside on the basis that such infringements are not by object anticompetitive and the Competition Authority had failed to prove effects (ComparetheMarket)


The UK Competition Appeal Tribunal (CAT) on 8 August 2022 set aside a £17.9 million fine against price comparison website Compare The Market, criticising the Competition and Markets Authority’s (CMA) legal and evidential assessment of the case. The CAT found that the CMA’s “anecdotal evidence” (...)

Jackie Holland, Henry Mostyn, Maurits J. F. M. Dolmans, Paul Stuart The UK Competition Authority calls for comments on draft guidance for new Vertical Agreements Block Exemption Order


The UK Competition and Markets Authority (the “CMA”) is consulting on its draft guidance (“Draft Guidance”) for its proposed Vertical Agreements Block Exemption Order (“VABEO”). It invites comments by May 5, 2022. The Draft Guidance largely maintains the status quo. There are, however, a number of (...)

Paul Stuart, John Messent, Henry Mostyn, Romi Lepetska The UK Government lowers the merger notification threshold for specific sectors including artificial intelligence, cryptographic authentication and advanced materials


On 21 July 2020, the Enterprise Act 2002 (Share of Supply) (Amendment) Order 2020 and the Enterprise Act 2002 (Turnover Test) (Amendment) Order 2020 came into force. Both Orders amend the jurisdictional thresholds for mergers in certain sectors. Under the new rules, the thresholds have been (...)

Paul Gilbert, Henry Mostyn, Romi Lepetska, Richard Pepper The UK Supreme Court dismisses the two largest payment processing networks’ arguments on the basis that their multilateral interchange fees restricted competition but upholds grounds of appeal concerning the application of the “passing on” defense (Sainsbury’s / Visa / MasterCard)


On 17 June 2020, the Supreme Court handed down a much anticipated judgment concerning the default multilateral interchange fees (MIFs) set by Mastercard and Visa (together, the Appellants). The case considered appeals relating to three separate damages actions brought by retailers against the (...)

George S. Cary, Maurits J. F. M. Dolmans, Bruce Hoffman, Thomas Graf, Leah Brannon, Richard Pepper, Henry Mostyn, Alexis R. B. Lazda, Savannah Haynes, Kristi Georgieva, Jan Przerwa Exploitative abuses, price gouging & COVID-19: The cases pursued by EU and national competition authorities


The COVID-19 pandemic has led to extreme demand and price volatility for certain products, as well as fluctuations in firms’ costs. As firms struggle to manage these changes, agencies are aggressively seeking to show they are preventing consumer exploitation—for example, as a result of (...)

7075 Review

Frédéric Jenny, Damien Neven, Jacques Buhart, David Henry, Thomas Funke, Mathew Heim, Catarina Midões, Nicholas Levy, David Little, Henry Mostyn, Ioannis Lianos, Massimo Motta, Martin Peitz, Cristoforo Osti, Almos Papp, Christian Wik, Kristian Hugmark, Julia Vahvaselkä, Antoine Winckler, Thierry Boillot Which competition and industrial policies for the new EU Commission after Siemens/Alstom?


This series of articles presents different points of view about the priorities of the newly established Commission on competition policy in Europe in the aftermath of the decision prohibiting the Siemens/Alstom merger and of the manifesto published by French and German governments. These (...)


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