'I would pick out three particular individuals I have worked with: ......Mark Stefanini, who offers a refreshing, down-to-earth and practical approach making him exceptionally user-friendly.'

Legal 500 2022


Mark Stefanini is a partner in Mayer Brown's London office, and a member of the Firm’s global International Arbitration & Litigation, Cybersecurity & Data Privacy and Energy Practices. He leads the Energy Disputes team in London. He acts for energy companies, financial institutions and other large corporations in a wide range of disputes frequently involving a multi-jurisdictional element. He also advises clients on their response to cyber incidents including malware attacks and data breaches and is experienced in working with international clients to co-ordinate their response across a range of jurisdictions.

Mark handles major disputes and cybersecurity incidents for clients in a variety of sectors including the energy, financial services, chemicals, technology, shipping and automotive sectors. He regularly acts in disputes involving complex issues of contractual interpretation, misrepresentation and the existence or scope of tortious duties. He has particular experience in financing disputes, warranty claims, claims relating to MAC or force majeure and other post-acquisition disputes, supply chain disputes, shareholder and JV disputes, competition related claims and breach of confidence claims. He regularly advises oil and gas companies on issues arising out of disputes with regulators, the sale or purchase of assets, JOAs, farm-out arrangements and other commercial disputes.

Mark regularly counsels senior management on cybersecurity risks and is experienced in managing related litigation to mitigate the impact on businesses. He is commercially focused and is experienced in using mediation and a range of other alternative dispute resolution techniques to provide results for clients at the earliest opportunity. He regularly advises on dispute resolution agreements to be included in cross-border transactions, including transactions involving sovereign entities. He has acted in substantial trials in the Commercial Court and Chancery Division as well as before the Court of Appeal and Supreme Court. He is also experienced in acting for clients before a wide range of arbitral institutions (including the ICC, SCC, LMAA and LCIA).

Spoken Languages

  • English



  • Acted as lead counsel for a multinational company in an LCIA arbitration relating to the purchase of a substantial industrial facility together with related hydropower and port facilities.  The dispute concerned liability for certain post completion payments and maintenance of the hydropower facilities.
  • Advising oil & gas companies in response to regulatory challenges and related litigation concerning UKCS assets
  • Acting for an oil & gas company on indemnity claims arising out of the sale of UKCS assets to an international investor
  • Advising an oil & gas company on warranty claims arising out of an acquisition in South America
  • Advising an oil & gas company in relation to a dispute with its former CEO and local partner
  • Acting for a listed oil & gas company in relation to disputes with its local JV partner arising out of operations in Nigeria.
  • Acting for a listed oil & gas company in relation to disputed exclusivity under a crude oil purchase agreement.
  • Acting for an oil company in relation to disputes under various crude handling and offtake agreements and related charterparties.
  • Defended a parastatal oil company in four related arbitrations (under LMAA rules) arising out of exploration and production activities offshore Brazil.
  • Advising a major shipping group on disputes arising out of the operation of its fleet of LNG carriers.
  • Advising the sellers of a windfarm in litigation arising out of alleged breach of warranties associated with the grid code.

Cybersecurity/Incident Response

  • Advising a global financial institution in relation to a data breach. Obtaining appropriate urgent injunctive relief against persons unknown responsible for the theft of data and implementing international process for compliance with notification and other obligations pursuant to GDPR and other relevant international standards.
  • Advising several private equity funds in relation to a cross-border cybersecurity incident affecting a global business.
  • Regularly guides senior management as they prepare for and respond to complex cyber incidents and supply chain attacks.

Financial Services

  • Acting for Société Générale in the Court of Appeal, successfully reversing a first instance order providing for an inquiry as to damages arising out of the maintenance by Société Générale of freezing injunctions against various Goldas entities. Société Générale v Goldas Kuyumculuk Sanayi Ithalat Ihracat AS [2018] EWCA Civ 1093
  • Advising Spanish real estate investment fund in litigation concerning breaches of loan documentation and the construction of a London hotel.The case remains one of the leading authorities in relation to the interpretation of material adverse change provisions. Grupo Hotelero Urvasco SA v Carey Value Added SL (2012) QBD (Comm) (Court of Appeal – 12 October 2012). Grupo Hotelero Urvasco SA v Carey Value Added SL [2013] EWHC 1039 (Comm). 
  • Advising junior noteholder on claims arising from RMBS securitisation of Portuguese residential mortgages Cinnamon European Structured Credit Master Fund v. Banco Commercial Portugues SA [2009] EWHC 3381 (Ch); [2010] All ER (D) 209; (2009) 160 NLJ 30; [2010] I.L.Pr. 11.

Commercial Litigation and Arbitration

  • Acting for the Civil Aviation Authority in the Court of Appeal case that remains the leading English law authority on legal advice privilege, Civil Aviation Authority v R (on the application of Jet 2.com Limited) [2020 EWCA Civ 35]
  • Acting for a leading multinational food and beverage company in an ICC arbitration relating to breaches of contract affecting outlets across the Middle East.
  • Acting for a global technology company in relation to claims for breach of warranty arising out of the purchase of a cybersecurity business.
  • Acting in an ICC arbitration relating to the design and launch of various satellites.
  • Acting for the majority shareholders in a consumer products business in successfully resisting attempts by minority shareholders to disrupt a sale process.
  • Advised ship owners in relation to dispute with Chinese shipyard involving several shipbuilding contracts. 
  • Advised BASF on the first competition law case heard before the Supreme Court, securing a landmark decision on limitation periods. BCL Old Co Ltd and others v BASF SE (formerly BASF AG) and others (No 2) [2012] UKSC 45.
  • Advised pensions scheme trustees in substantial High Court proceedings against former professional advisers.
  • Represented a major music company in high-profile royalty disputes with Pink Floyd and The Beatles.
  • Acted for a sub-contractor on a multi-party professional negligence claim arising from the destruction of a major international retailer’s UK distribution centre in a fire. 
  • Represented an Israeli telecommunications company in a claim against a global mobile telephone operator arising from termination of an IT outsourcing contract.
  • Advised clients in the food, automotive, chemicals, construction and retail sectors in relation to product safety/liability issues including in relation to product recalls.


The London School of Economics and Political Science


  • England and Wales
  • Solicitor Advocate with Higher Rights of Audience (Civil)
  • Listed as a key lawyer for Banking Litigation, Commercial Litigation, International Arbitration and Insurance: Product Liability. (Legal 500 2023).
  • Listed as a key lawyer for Banking Litigation, ‘I would pick out three particular individuals I have worked with: ......Mark Stefanini, who offers a refreshing, down-to-earth and practical approach making him exceptionally user-friendly.‘ (Legal 500 2022).
  • Listed as a key lawyer for International Arbitration, Commercial Litigation and Fraud, Mark Stefanini 'is a down to earth but fierce litigator.' (Legal 500 2022).
  • Listed under 'Other key lawyers' for Banking Litigation, Commercial Litigation, Product Liability and International Arbitration. Mark Stefanini and Matthew Williams are shrewd litigators who traversed delicate issues concerning confidentiality with skill’ (Legal 500 2021).
  • 'Highly regarded' Mark Stefanini is listed as a key lawyer in four categories: Banking Litigation, Commercial Litigation, International Arbitration and Product Liability (Legal 500 2020).
  • Highly rated for commercial litigation and key adviser for international arbitration (Legal 500 2018).
  • Key name for commercial litigation and highly rated for international arbitration (Legal 500 2017).
  • Is recommended for commercial litigation and well regarded for international arbitration (Legal 500 2016).