Claire Jeffs

Joined firm 1998. Partner since 2005.

Claire is Co-Chair of the Competition Group globally and works in Slaughter and May’s Brussels and London offices.

Claire has extensive experience of both EU and UK competition law. She has been involved in a large number of high-profile merger cases before the EU and UK competition authorities, as well as coordinating merger approvals worldwide. On the contentious side, she has been involved in many cartel and other behavioural cases, including on appeal to the General Court in Luxembourg.

Highlights include advising:

  • Vodafone on its acquisition of parts of Liberty Global
  • Shire on its takeover by Takeda
  • Google in relation to the European Commission’s antitrust investigation into allegations that certain of its business practices in the search and advertising sectors violate European competition rules.

Claire has been named in [email protected]’s list of ‘40 in their 40s Notable Women Competition Professionals’ and The Lawyer’s Hot 100 list. She was awarded ‘Dealmaker of the Year’ by Global Competition Review in 2017, and shortlisted in the ‘Lawyer of the Year’ category in the 2019 Global Competition Review awards.

Claire is listed as a ‘Leading Individual’ by Chambers and The Legal 500, and recognised as a ‘Thought Leader’ in Who’s Who Legal: Competition. 

She is a member of the Brussels Bar (A list), as well as being qualified as a solicitor (England and Wales).

Claire is fluent in French and Russian and has good German.

Recent publications include:

  • Foreword, Concurrences e-Competitions Special issue, Dominance & Monopolization Research Program, June 2020. Available for subscribers here.
  • Introduction – Why E-commerce. An extract from the third edition of GCR’s E-Commerce Competition Enforcement Guide, first published in January 2019. The whole publication is available here.