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Sean Gammons specializes in the gas and power sectors. He has more than 20 years of experience advising energy companies and regulators on the design and operation of gas and electricity markets. His experience includes regulatory work on market rules, tariff design, and antitrust enforcement (such as merger approval and state aid), as well as commercial work on contract design, pricing, investment appraisal, and risk management. Mr. Gammons has led a large number of due diligence and valuation exercises in support of M&A transactions, greenfield investment, and financings in the UK, Europe, Middle East, North Africa, and Asia, covering deregulated, regulated, and hybrid (low-carbon) segments of the energy industry.


Examples of his advisory assignments include:

  • Advising a European gas incumbent on reform of its gas tariffs to meet various constraints (cost recovery, competition, and antitrust undertakings);
  • Advising RWE Npower and the Competition and Markets Authority on the reform of electricity transmission charges in the UK; and
  • Advising a European gas pipeline company on the development of a backhaul tariff based on market principles.

Mr. Gammons is also an experienced expert witness who has provided expert testimony in cases covering contractual disputes (construction, sale and purchase, M&A, and broker disputes, among others), antitrust matters, and energy industry regulation in a wide range of jurisdictions around the world, including the International Centre for Settlement of Investment Disputes (ICSID), the International Chamber of Commerce, and the English High Court. Examples of his expert work include:

  • Damages estimation for non-delivery of gas and/or electricity under long-term contracts, and related expropriation claims;
  • Economic analysis in relation to price re-opener and loyalty clauses in long-term contracts for gas, gas storage, and gas transport, including change of circumstances, market definition, and price re-sets;
  • Market definition and abuse of dominance review in relation to long-term contracts for gas storage and gas transport;
  • Liquefied natural gas (LNG) terminal and gas pipeline construction contract disputes; and
  • Assessing indemnification losses in relation to an SPA for the sale of a portfolio of wind farms.

Mr. Gammons is recommended as a leading energy expert by Who's Who Legal (2019–2023) and lauded as an expert with a “wealth of experience in the energy sectors, spanning regulatory work in market rules, tariff design, and antitrust enforcement.” Mr. Gammons is praised for his “great analytical skills” and his “very good command of the legal aspects of the case.”


  • MSc in economics, University College, London
  • Diplôme d’Ingénieur, Ecole nationale supérieure du pétrole et des moteurs (ENSPM), Paris
  • BA, with honors, Oxford University


In Who’s Who Legal: Energy Experts 2023, Mr. Gammon’s clients recognized:


  • He “ranks prominently for his first-rate energy practice,” and
  • He has received “widespread endorsements as ‘a very strong adviser and one of the big players in the field.’”