Matthieu practices international arbitration, commercial dispute resolution and public international law. Prior to joining the Bar, Matthieu qualified as a New York attorney in 2011 and worked as an associate in the international arbitration team of Cleary Gottlieb, Steen & Hamilton, in Paris and as a consultant for the World Bank.
Matthieu was appointed to the Attorney General’s Public International Law C Panel of Counsel in 2017.
Current and recent representative experience includes:
- Acting as junior counsel for the intervening parties in R (Miller & others) v Secretary of State for Exiting the European Union  EWHC 2768, and before the Supreme Court in R(Miller & others) v Secretary of State for Exiting the European Union  UKSC 5 (led by Patrick Green QC and Henry Warwick);
- Acting as sole counsel in two LCIA arbitrations arising out of sale of goods contracts for ethyl and fuel alcohol (details not public);
- Acting as junior counsel for the First Claimant in the enforcement proceedings arising out of the Award in Micula & Others v Romania:  EWHC 31 (Comm) (led by Sir Alan Dashwood QC and Patrick Green QC);
- Acting for the claimants in City-State N.V. et al. v Ukraine, ICSID Case No. ARB/14/9, a dispute under a bilateral investment treaty in relation to various breaches of the treaty (led by Stephen Fietta);
- Acting as sole counsel for a Ukrainian company in a commercial arbitration pursuant to the ICC Rules in relation to a dispute under a contract in the telecommunications sector (details not public);
- Acting as junior counsel for the Claimant in arbitration commenced under the ECT and governed by the SCC rules in the energy sector in relation to breaches by an Eastern European State of the ECT (details not public);
- Acting as junior counsel for the Claimant in an arbitration commenced pursuant to a bilateral investment treaty and the SCC rules in the banking sector in relation to breaches by an Eastern European State of the BIT (details not public, led by Matthew Weiniger QC and Stephen Fietta);
- Advising a party in potential challenge proceedings following a bilateral investment treaty arbitration award (details not public, with Stephen Fietta);
- Acting as junior counsel for the Respondent in Tethyan Copper Company Pty Limited v Islamic Republic of Pakistan, ICSID Case No. ARB/12/1, and Tethyan Copper Company Pty Limited v Province of Balochistan, ICC Case No. 18347/VRO/AGF, arbitrations arising out of the refusal of a mining licence over copper and gold deposits at Reko Diq, in Pakistan (led by Graham Dunning QC and Cherie Blair QC);
- Advising a multinational company on enforcement proceedings in various jurisdictions following a successful £8 million ad hoc award (confidential);
- Advising an international organization on drafting an arbitration agreement with a series of contractors for waste management (confidential);
- Acting as junior counsel for a Defendant in Chevron Corporation v Amazonia Recovery Limited & others (Supreme Court, Gibraltar), complex proceedings concerning alleged commercial conspiracy arising from US$18 billion judgment in respect of environmental pollution in Ecuador with associated arbitration proceedings (the Chevron v Ecuador BIT proceedings) and proceedings in New York and elsewhere (led by Vernon Flynn QC (Essex Court Chambers), Patrick Green QC (Henderson Chambers) and Jonathan Adkin QC (Serle Court) and Henry Warwick);
- Acting as junior counsel in a 6-week trial brought by the HSE against an aerospace company raising significant issues in relation to parent company liability (R v CAV) (led by Prashant Popat QC);
- Appearing as sole counsel in numerous civil matters (including, but not limited to, commercial, product liability, consumer credit, property and landlord/tenant disputes) before County Courts and the High Court.