"he is very thorough and knowledgeable"
Chambers Global 2020


David Harrison is a partner in the London office. He leads the European Antitrust and Competition team and is one of the group leaders of the global Antitrust practice. He has practised competition law for over 27 years in London and Brussels, and has advised numerous major global corporations in a wide range of sectors.

He has represented parties to some of the largest global cartel investigations of recent years, including the European Commission’s investigations concerning automotive parts, foreign exchange and freight forwarding, as well as various national investigations within the European Union and other jurisdictions worldwide.

His merger control experience includes advising on many high profile cases, obtaining clearance of numerous transactions under the EU Merger Regulation and UK merger control rules, and co-ordinating complex multi-jurisdictional cases.

David also advises on abuse of dominance, complaints, compliance and litigation at EU and national level, and on the application of the competition rules in regulated sectors. He has extensive State aid experience, including in relation to major infrastructure and public sector projects, and has advised on a wide range of other aspects of EU law.

Prior to joining Mayer Brown in 2015, David established and headed for ten years the EU and Competition practice of another international law firm, based in London. He worked in Brussels from 1996-2005 with another global law firm, as a partner from 1998-2005.

Spoken Languages

  • English
  • French
  • German



  • Represented a major Japanese automotive parts supplier in relation to the European Commission’s wire harness investigation, a related UK criminal investigation and other investigations worldwide.
  • Advised a global investment bank on the competition aspects of the foreign exchange investigations by various authorities.
  • Represented an international freight forwarding group in relation to a worldwide series of cartel investigations.
  • Advised on various national cartel investigations (e.g. construction, construction materials, sports goods retailing, CD pricing), and in relation to cartel investigations outside the EU.

Merger control

  • Advised a third party on its intervention in relation to the Deutsche Börse/NYSE Euronext merger, which was prohibited by the European Commission.
  • Advised an international nickel producer on the European Commission’s Phase II investigation of its $20bn hostile bid for a rival producer.
  • Obtained clearance of many transactions under the EU Merger Regulation since its introduction in 1990, and advised on numerous multi-jurisdictional merger control matters.
  • Obtained unconditional clearance from the UK Competition Commission in relation to a completed merger in the retail sector.

Abuse of dominance

  • Advised a third party on Ofgem’s metering inquiry, which resulted in the highest UK fine for abuse of dominance.
  • Advised on various complaints, including by a communications company against BT to Ofcom, and to the Office of Fair Trading in respect of alleged abuse of dominance in relation to online advertising.

Competition litigation

  • Sports Direct v. Competition Commission (UK Competition Appeal Tribunal, 2009). Successfully challenged the Competition Commission in the CAT on a point of due process.
  • Advised on the defendant and claimant side in relation to various actual or contemplated follow-on damages claims, within and outside the EU.


  • Advised on joint ventures, other collaborative arrangements and distribution in a wide variety of sectors.
  • Advised numerous organisations on managing competition law risk, including through the development and implementation of compliance programmes, internal audits, training and dawn raid preparedness, and advised on the development of commercial strategies in the light of the rules on dominance.

Sector investigations

  • Advised a party to a UK sector investigation concerning contact lens solutions.
  • Advised a third party in relation to the Competition Commission’s airports inquiry.

Regulated sectors

  • Advised on mergers in the energy sector under the EU and UK merger control rules, and advised an industry association on the creation of new post-trade infrastructure for the UK wholesale energy sector.
  • Advised various international airlines on competition and regulatory matters, and advised in relation to the proposed creation and acquisition of airports.

State aid

  • Advised on the State aid aspects of the creation of many of the facilities for the 2012 London Olympics.
  • Advised sponsors and lenders on a variety of major infrastructure projects, e.g. Athens Airport, the Thessaloniki Metro and the D47 Road (Czech Republic).

EU regulation

  • Advised on an application for interim measures in the European Court of Justice against the EU Council for breach of the public procurement rules.
  • Advised non-EU companies on establishment of operations in the European Union.


Magdalen College, Oxford, (Open Exhibition) MA Jurisprudence

Université Libre de Bruxelles, Licence Spéciale en Droit Européen


  • England and Wales


  • Member of the EU Law Committee of the Law Society of England & Wales from 2002-12.
  • Member of the Joint Working Party on Competition Law of the Bars and Law Societies of England and Wales.
  • Member of the Steering Committee of the UK State Aid Law Association.
  • American Bar Association.
  • David Harrison of Mayer Brown LLP has a particular focus on merger clearance matters. Sources highlight his "understanding of hi-tech elements and ability to pursue lots of international dimensions at once." Harrison also represents clients in CMA and European Commission investigations. Chambers Europe (2020).
  • Listed as a 'Leading Individual' for competition law. David Harrison handles merger control matters for private equity and corporate clients, having acted on deals across various sectors. He also advises on investigations, responses to information requests and complaints to competition regulators. Sources say that "he is very thorough and knowledgeable." Chambers UK and Chambers Global (2020).
  • David Harrison has a particular focus on merger clearance matters. Sources highlight his "understanding of hi-tech elements and ability to pursue lots of international dimensions at once." Harrison also represents clients in CMA and European Commission investigations. Chambers UK (2019)
  • The team at Mayer Brown International LLP is noted for its "specialist market knowledge". David Harrison co-heads the firm’s European antitrust and competition practice. Legal 500 UK (2018)
  • David Harrison heads the "very solid" team at Mayer Brown International LLP, which is noted for its "broad experience" and "creative approach". Legal 500 - EU and competition (2017)
  • David has been consistently ranked for many years as a leading competition lawyer in the Legal 500, Chambers, the Global Competition Review Who’s Who of Competition Lawyers and other Directories.
  • "tenacious and very focused on doing the best for his client." Chambers UK (2013)
  • “exceptionally able, with a thorough grasp of both strategy and detail.” Legal 500 UK (2012)
  • “exemplif[ies] the firm’s approach to client care and management, and [is a] lawyer[s] of a very high calibre.” Legal 500 UK (2011)
  • “in-depth knowledge” and a “good appreciation of the broader issues.” Legal 500 UK (2010)
  • “his strong work ethic and impressive grasp of the issues surrounding international cartel investigations.” Chambers UK (2009)
  • “goes the extra mile”, “quickly gets to the heart of the matter” and is “tenacious”. Legal 500 UK (2009)