London partner Jeff Sullivan KC is a member of the International Dispute Resolution Group and Co-Chair of International Arbitration in Europe. Mr. Sullivan’s practice focusses on international arbitration and public international law.

Mr. Sullivan is one of the market’s leading and most respected advocates, representing clients in commercial and investor-state arbitrations before all the major arbitral institutions. He also regularly sits as an arbitrator, and advises clients in all aspects of public international law.

Mr. Sullivan has advised clients from a range of sectors and regions, but has a particularly deep practice focussed on disputes in the energy, extractive industries and infrastructure sectors.

His experience includes disputes involving long-term supply agreements, concession agreements, production sharing and operating agreements, joint venture agreements, EPC and other construction agreements.

Mr. Sullivan has also acted as counsel and lead advocate in more than 30 bilateral investment treaty and Energy Charter Treaty arbitrations, and has advised nation states in Europe, Central Asia and the Middle East on the negotiation and drafting of trade and investment treaties.

Recent experience includes a $4 billion ICC arbitration centred on a Middle Eastern infrastructure project; an UNCITRAL arbitration concerning a $750 million transport project dispute; acting for 25 investors in renewable energy projects in 10 separate ICSID and UNICTRAL arbitration claims against the Kingdom of Spain under the Energy Charter Treaty involving claims in excess of $2.5 billion; and two parallel LCIA arbitrations with the amount in dispute in excess of $2.2 billion.

Mr. Sullivan is consistently noted as a leader in his field by the major legal directories. The Legal 500 UK names him in its Hall of Fame for International Arbitration, and he is also listed as a leading individual for Public International Law. Chambers Global, Chambers Europe and Chambers UK describe him as “superb all around” and “a strong advocate.” The guides have further noted that he is “a fantastic lawyer [who is] calm, smart and strategic. His ability to understand what the client needs is terrific.”Mr. Sullivan is also recognised as a Thought Leader by Who’s Who Legal (2024).

Mr. Sullivan is a Member of the ICC UK Arbitration & ADR Nominations Committee, a member of the Energy Charter Treaty Secretariat’s Legal Advisory Task Force, an Executive Board Member of the European Federation for Investment Law and Arbitration and an Executive Committee Member of the Foundation for International Arbitration Advocacy.


  • University College London, 2006, LL.M.
  • University of Florida Levin College of Law, 1999, J.D.
  • University of Florida, 1996, B.A.

Bar Admissions

  • District of Columbia
  • Solicitor, England & Wales