Three Crowns has maintained its status as a top tier firm and has been ranked in band one for both Commercial Arbitration and Investor-State Arbitration in the Chambers UK 2024 rankings. Constantine Partasides KCGaëtan Verhoosel KCReza Mohtashami KC, and Carmen Martinez Lopez have been individually ranked. The firm also maintained its leading ranking in the Public International Law guide.


Chambers highlights that Three Crowns is “an acclaimed international arbitration outfit with an impressive client roster” with “expertise in both commercial arbitrations and investor-State disputes”. One source emphasises that “Three Crowns’ partners are unquestionably among the world’s leading international arbitration practitioners”, with another adding that the team is “profoundly sophisticated in their approach”. Another commentator highlights the “highly professional team”, noting that they are “very responsive and have the ability to foresee the next step”.

The firm has also been recognised for its work in public international law, with the guide highlighting its “strong pedigree in public international law matters” and that “the firm fields a bench of highly esteemed practitioners in this area”.



Constantine is one of only two practitioners identified as a “Star Individual” in the arbitration guide, the highest ranking in Chambers. The publication describes him as a “highly esteemed arbitration specialist acting for top-echelon clients”, also emphasising his “capabilities as arbitrator”. One source notes that “Constantine is one of the best professionals in this field globally”, with another adding that “his knowledge of the arbitration process is unparalleled” and “he is an outstanding oral advocate with an authoritative presence”. A third notes that Constantine “is a pre-eminent advocate” who “excels at legal analysis, oral advocacy and hearing strategy”. He has also been ranked for his work in public international law with Chambers noting that he is “well known for acting in high-value disputes under bilateral and multilateral investment treaties around the world”. Constantine has appeared as counsel in some of the largest commercial arbitrations of the past decades and his broad practice includes inter-State and investment treaty disputes. He is a Member of the ICCA Governing Board and a Director of the LCIA Board.


Gaëtan maintains his band one ranking in this year’s arbitration edition, with Chambers highlighting that he “has earned an excellent reputation”. One source emphasises that he “is very experienced professional who is able to understand the client’s needs and lead a team to deliver tailored legal advice”. Sources also note that Gaëtan “provides excellent support”, with another adding that he “performs very well with respect to briefing strategies, legal arguments and strategic decisions”. Gaëtan is also recognised for his work in public international law. He has served as advocate and as arbitrator in numerous commercial and investment treaty arbitrations where significant financial recoveries were at stake or novel legal issues raised. He is a member of the SIAC Court of Arbitration and was appointed to the ICSID Panel of Arbitrators by the Kingdom of Belgium.


In maintaining his ranking again this year, Chambers notes that Reza acts in “high-value disputes” with a “particular focus on the Middle East”. One source comments that Reza “is an eloquent, formidable and gracious advocate”, adding that he “is exceptionally talented at simplifying issues for tribunals”. Another source highlights that he is a “very meticulous lawyer” with “a strong commercial acumen and vision”, noting that he is “very impressive during hearings”. He has represented clients as counsel and advocate in more than 90 arbitrations conducted under a variety of arbitration rules in many different jurisdictions. Reza has particular expertise in disputes arising in emerging markets and is a highly sought-after specialist in the Middle East, with a focus on the telecoms, energy, and infrastructure sectors.


Carmen has moved up a ranking in this year’s guide, in which Chambers highlights that she is “credited for her Latin American expertise” and “sought out for her knowledge of Spanish law matters”. A commentator describes her as “very well respected”, with Chambers adding that she is “experienced in handling significant arbitrations in the oil and gas sector, often brought against sovereign States”. Carmen has appeared as advocate in numerous investment treaty and commercial arbitrations, both under the rules of the major arbitral institutions and ad hoc, across a variety of jurisdictions.

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