Thomas Masterman


Tom has over 15 years’ experience advising clients on complex international, EU and UK merger clearances, including some of the highest-profile M&A transactions in the market in recent years. 
He also has an established track record of advising on cartel and abuse of dominance investigations, national security / foreign direct investment reviews and market investigations. Tom’s practice spans a broad range of sectors, with particular expertise in infrastructure, life sciences and TMT. Tom is listed in the Legal 500 directory as a “rising star” and a “superb competition lawyer”. He is also ranked as “future leader” by Who’s Who Legal, who note that he “combines deep industry knowledge with top-drawer intellect to solve client problems.”


Representative matters

GBP31bn: A multinational telecommunications company on its joint venture with Telefónica SA to merge Virgin Media and O2.

USD71bn: 21st Century Fox on its acquisition by The Walt Disney Company and on its takeover bid for Sky.

USD3.6bn: A shipping company on its acquisition of LF Logistics from Li & Fung.

Hitachi on various global cartel matters, including the LCD, CRT, GIS, Power Transformers and Auto-Parts investigations.

Published Work

  • Philip Mansfield, Thomas Masterman, Imogen Carr (2022) “Global antitrust enforcement report”, Allen & Overy LLP
  • Thomas Masterman (2021) “FTC launches multilateral working group with EU, UK and Canadian antitrust authorities to take tougher stance on pharmaceutical mergers”, Allen & Overy LLP
  • Philip Mansfield, Thomas Masterman, Imogen Carr (2021) “Global antitrust enforcement report”, Allen & Overy LLP
  • Thomas Masterman (2020) “European Commission completes current cycle of pay-for-delay probes with fines imposed on Teva and Cephalon”, Allen & Overy LLP

Leadership Positions And Professional Affiliations

Member, Law Society of England and Wales.
Thomas Masterman receives glowing praise as being “pragmatic and cerebral while also having a deep sectoral knowledge”, particularly in areas such as mass media and telecoms. Peers and clients say: “He has been great on various important M&A transactions.” “Tom is a fantastic lawyer with deep knowledge and experience on a wide range of competition issues.” “He is able to combine industry knowledge with a top-drawer intellect to solve client problems”.
Who’s Who Legal, 2020
"Thomas Masterman is excellent with merger control work" report peers. In particular, they add "His knowledge in the media and entertainment sector is phenomenal".
Who’s Who Legal, 2019


  • Top 3, Global Elite firms, Global Competition Review 2020
  • TMT Firm of the Year, Legal 500 UK Awards 2019
  • Competition Team of the Year, British Legal Awards 2018
  • Competition Team of the Year, Legal Business Awards 2017
  • GCR Behavioural Matter of the Year Europe 2016



Admitted as solicitor, England and Wales, 2006

Admitted as solicitor, Ireland, 2016


BA, European Legal Studies, Durham University

Erasmus Programme, Katholieke Universiteit Leuven

A&O Shearman was formed on May 1, 2024 by the combination of Shearman & Sterling LLP and Allen & Overy LLP and their respective affiliates (the legacy firms). Any matters referred to above may include matters undertaken by one or more of the legacy firms rather than A&O Shearman.