Leonidas Theodosiou advises on antitrust, foreign direct investment (FDI), and regulatory matters, having practiced in London and Brussels for more than a decade. He is highly recommended by leading directories in the “EU and Competition” and “Competition Litigation” categories, and has been identified by The Legal 500 as one of the UK’s leading “Next Generation Partners” in the area of competition law. Leo is also recognized by Global Competition Review as one of the world’s Top 40 Lawyers Under 40 in FDI regulation. Clients have praised his “extensive international capabilities” and described him as “extremely skilled and responsive.” Leo is one of few lawyers globally who are fully qualified to practice law in the United Kingdom, the European Union, and the United States.
Leo is a partner in Morgan Lewis’s “Highly Commended” competition team in London (The Lawyer Awards, 2021, 2022). He advises on all aspects of UK, EU and international competition law and competition litigation. He additionally counsels clients on FDI matters as well as on EU state aid control, EU foreign subsidies control, and the UK regulation of subsidies.
Leo is recommended by The Legal 500 UK for both competition law and competition litigation. In relation to competition litigation, Leo is “noted for his extensive international capabilities” and praised for being “extremely skilled and responsive, and [for] bring[ing] a real depth of experience in this complex and challenging area.” In relation to transactional matters, clients say he offers “excellent support and is always on hand during a transaction to offer top class insights which allow for clear and fully informed decision making.”
In 2021, Leo was featured in the Festival of Talent edition of The Lawyer for his contribution in securing Sainsbury’s victory in the UK Supreme Court in its interchange fee litigation against Visa. He is a member of the Morgan Lewis team that was awarded Behavioural Matter of the Year—Europe, Challenges to CMA Search Warrants, by Global Competition Review in 2018.
Prior to joining Morgan Lewis, Leo spent several years practicing with a Magic Circle law firm, resident in Brussels. In 2018, Leo was seconded to Tata Steel—one of the world’s largest steelmakers—where he served as the organization’s in-house counsel dedicated to antitrust.
Leo holds postgraduate degrees in law from Harvard Law School and the University of Cambridge (Trinity Hall). He has received significant awards and fellowships in recognition of his research and academic achievements, including a Fulbright Fellowship by the US Department of State, and was selected to deliver the 2013 Commencement Speech at Harvard Law School.
Leo is the vice chair of the American Bar Association’s Privacy and Information Security Committee. He frequently speaks and writes about data protection issues, in particular in the context of mergers and acquisitions (M&A) transactions and the interplay between antitrust and data protection.Competition Litigation
Merger & FDI Control
Antitrust Investigations
State Aid Control
Shortlisted, Financial Times Innovative Lawyers Awards Europe (2023)
Recognized, 40 Under 40, Global Competition Review FIC (2023)
Next Generation Partner, Corporate and commercial: EU and competition, The Legal 500 UK (2024)
Recommended, Dispute Resolution: Competition Litigation, The Legal 500 UK (2023, 2024)
Recommended, Corporate and Commercial: EU and Competition, The Legal 500 UK (2023)
Vice Chair, ABA Committee on Privacy & Information Security
Highly Commended, Competition Team of the Year, The Lawyer Awards (2021, 2022)
Member, Behavioural Matter of the Year—Europe, Challenges to CMA Search Warrants, Global Competition Review (2018)
Member, Practice Group of the Year, Competition, Law360 (2017–2021)
Member, Law Society of England and Wales (Competition Section)
Fulbright Fellow, US Department of State (2012–2013)