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.
extremely skilled and responsive
The Legal 500 UK
has [a] great understanding of our business and is able to provide meaningful advice.
The Legal 500 UK
has an attention to detail that means you know he has explored all reasonable avenues in looking for solutions.
The Legal 500 UK
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.
Concordia in connection with the first-ever court challenge of CMA search warrants at the High Court and the Court of Appeal
Sainsbury’s Supermarkets in relation to its claim against Visa for competition damages arising out of Visa’s UK multilateral interchange fees
Numerous merchants in the retail, transport, and hospitality industries in relation to their claims for competition damages against Visa and Mastercard arising out of UK and EEA multilateral interchange fees imposed by Visa and Mastercard, respectively
Focus Pharma on its appeal in the Competition Appeal Tribunal (CAT) against the CMA’s infringement decision alleging that it participated in a market sharing agreement in relation to anti-nausea drug Prochlorperazine
Mercury Pharma on its appeal in the CAT against the CMA’s infringement decision alleging that it abused its market dominance by charging unfair and excessive prices in relation to thyroid drug Liothyronine
AMCo on its appeal in the CAT against the CMA’s infringement decision alleging that it was party to a market exclusion agreement in relation to adrenal insufficiency drug Hydrocortisone
A leading operator of games of chance in a number of state aid related proceedings before the General Court and the Court of Justice of the European Union (including in T-416/13, Stanleybet v. Commission; T-57/13 and T-58/13, Casino Loutraki, others v. Commission; and subsequent appellate proceedings in C-131/15)
Merger & FDI Control
One of the world’s largest private equity firms on the merger and FDI control aspects of numerous contemplated or completed investments indicatively including:
the $5.3 billion SPAC transaction to take public a global travel operator
the $7.1 billion acquisition of an automotive parts manufacturer
the $5.2 billion acquisition of a leading air cargo company
the acquisition of a stake in a leading telecommunications company in the context of its Chapter 11 reorganization and recapitalization
the $3.7 billion combination of the ridesharing businesses with that of Uber in various countries
its $1 billion acquisition of various interests held by Uber in their formerly joint FoodTech, delivery, and self-driving businesses
MSP Sports Capital on its acquisition of a stake in McLaren Racing
Advanz Pharma on various transactions including its acquisition of (i) a portfolio of antiepileptic medicines from Eisai; and (ii) a portfolio of alprostadil products from UCB
Tata Steel on merger control aspects of various transactions
Abbott Laboratories on its $2.9 billion acquisition of CFR Pharmaceuticals
Pfizer on global merger control aspects of various multibillion dollar transactions
The Carlyle Group on the acquisition of a 36.8% stake from General Electric in Hong Kong listed satellite operator AsiaSat for up to $483 million
Citigroup in relation to a Phase II merger control investigation into the sale of Citigroup’s retail network in Greece to Alpha Bank
Hellenic Petroleum and the Greek Privatization Agency in relation to the European Commission’s Phase II investigation into the proposed acquisition of the Greek Gas Transmission System Operator DESFA by SOCAR
A major games of chance operator in relation to a Phase II merger control investigation into the acquisition of exclusive rights to operate horse-racing betting
A major investment management company on the acquisition of stakes in a number of Europe’s leading games of chance operators (including Casinos Austria and the Czech lottery company Sazka)
A leading defence company on the CMA’s investigation into suspected bid rigging in relation to Home Office contracts for the operation of immigration detention and deportation centers at Heathrow Airport; case closed by the CMA
AMCo on its defence against a Statement of Objections (SO) and a Supplementary Statement of Objections (SSO) by the CMA regarding an alleged pay-for-delay arrangement with respect to adrenal insufficiency drug Hydrocortisone
Mercury Pharma on its defence against the CMA’s SO and SSO and Supplementary SSO in relation to alleged unfair and excessive pricing of thyroid drug Liothyronine
Focus Pharma on its defence against the CMA’s SO in relation to an alleged market exclusion arrangement in respect of anti-nausea drug Prochlorperazine
Advanz Pharma on its defence against the CMA’s SO in relation to an alleged market sharing arrangement in respect of antibiotic Nitrofurantoin
A global manufacturing corporation on (i) its internal investigation of suspected antitrust violations; (ii) its application for immunity or leniency to antitrust enforcement agencies; and (iii) designing and implementing its organisation-wide compliance programme
A global electronics corporation in a major cartel investigation involving immunity applications in multiple jurisdictions in respect of various electronic components
State Aid Control
A Member State’s privatization agency on state aid control aspects of a number of landmark privatizations, including (i) the extension of the concession for the operation of the country’s largest airport for €1.1 billion; and (ii) the contemplated divestment of the majority of shares in the country’s natural gas transmission incumbent
Successfully defended Citadele Bank on an in-depth investigation launched by the European Commission concerning allegedly illegal state aid
An international conglomerate on two state aid investigations into allegedly unlawful infrastructure aid
A major games of chance operator in relation to multiple state aid investigations
Spanish, Dutch, and Greek banks which benefitted from state aid on negotiating, implementing and/or amending their restructuring plans in line with EU state aid control rules
Harvard Law School, 2013, LL.M., Fulbright Fellow, US Department of State
University of Cambridge, Trinity Hall, 2012, LL.M.
Aristotle University of Thessaloniki, Greece, 2011, LL.B.
England and Wales (Solicitor)
General Court and Court of Justice of the European Union
Greece: Courts of Appeal
Greece: Supreme Court
Awards and Affiliations
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)