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 2023 rankings. Constantine Partasides KC, Gaëtan Verhoosel KC, Reza 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 boutique with an impressive client roster” with “expertise in both commercial arbitrations and investor-State disputes”. One source notes “they’re a Rolls-Royce arbitration firm – they have really top-quality people” with another adding “the team has a great ability to handle highly complex arbitrations, as well as annulment proceedings”. Another commentator emphasises that “Three Crowns provides practical and workable commercial solutions”, with another adding “they’re all very knowledgeable, easy to work with, and provide robust advice”.

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 he “is one of the best, most eloquent lawyers”, adding “he’s smooth and tribunals just sit back and enjoy listening to him”. Another added “he’s extremely good at identifying creative solutions to complex legal issues”, with a third noting “Constantine is a class act”. 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 has moved up to band one in this year’s arbitration edition, with Chambers highlighting that he “has earned an excellent reputation”. One source comments “he is without doubt one of the best professionals out there”, adding “he has world-class experience and skill”. Another emphasises that Gaëtan’s “delivery is extraordinary – he is beyond sophisticated and professional”. A third commentator notes that he is “very practical and develops robust strategies. He’s also an excellent advocate”. 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, a source comments “Reza has great legal judgement” with another adding “he’s a really sharp lawyer”. Chambers notes that Reza acts in “high-value disputes” with a “particular focus on the Middle East”. 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 maintained her ranking again this year, in which she is “credited for her Latin American expertise” and that she is “sought out for her knowledge of Spanish law matters”. A commentator describes her as “a talented lawyer”, with Chambers adding that she is “experienced in handling significant arbitrations in the oil and gas sectors, 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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