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Contact

Contact with chambers should be made through the Practice Management Team. They are happy to discuss client requirements and provide further information on such matters as the expertise and experience of individual members, fees, working practices and languages spoken. We have members able to work in French, German, Italian, Spanish, Dutch, Swedish, Greek and Chinese (Mandarin).

Outside working hours, a member of our team is always available to be contacted on matters of an urgent nature. Contact should be made using the Chambers main number or email.

To contact our Singapore office, please contact our BD Director, Asia, Rachel Foxton. Out of office hours calls will automatically be diverted to our clerking team in London.

London

20 Essex Street
London
WC2R 3AL

enquiries@twentyessex.com
t: +44 20 7842 1200
DX 0009 Lond/Chan Lane

Singapore

28 Maxwell Road
#02-03
Maxwell Chambers Suites
Singapore 069120

singapore@twentyessex.com
t: +65 62257230

Contact

Contact with chambers should be made through the Practice Management Team. They are happy to discuss client requirements and provide further information on such matters as the expertise and experience of individual members, fees, working practices and languages spoken. We have members able to work in French, German, Italian, Spanish, Dutch, Swedish, Greek and Chinese (Mandarin).

Outside working hours, a member of our team is always available to be contacted on matters of an urgent nature. Contact should be made using the Chambers main number or email.

To contact our Singapore office, please contact our BD Director, Asia, Rachel Foxton. Out of office hours calls will automatically be diverted to our clerking team in London.

London

20 Essex Street
London
WC2R 3AL

enquiries@twentyessex.com
t: +44 20 7842 1200
DX 0009 Lond/Chan Lane

Singapore

28 Maxwell Road
#02-03
Maxwell Chambers Suites
Singapore 069120

singapore@twentyessex.com
t: +65 62257230

Simon Olleson

Simon Olleson

Call: 2002

English (fluent); Italian (proficient); French (proficient)

Simon’s practice focuses on public international law and international arbitration (including both investment protection disputes and international commercial arbitration).

He has particular experience as counsel and advocate in inter-State disputes, including before the International Court of Justice (ICJ), the International Tribunal for the Law of the Sea (ITLOS) and international arbitral tribunals constituted under the auspices of the Permanent Court of Arbitration (PCA).

Simon has advised and acted in a broad range of international disputes involving: issues of State responsibility and treaty interpretation, territorial disputes, investment protection disputes (including claims before the International Centre for the Settlement of Investment Disputes (ICSID), and arbitral tribunals under the PCA and UNCITRAL Rules), issues of international human rights law, issues of sovereign immunity, disputes involving State succession, and disputes involving issues under the law of the sea (including maritime delimitation).

He also has substantial experience in international commercial arbitration and has acted in cases brought under a variety of procedural rules (UNCITRAL, LCIA, ICC, Stockholm Chamber of Commerce, CIArb, etc).

Simon also has experience of litigation before the English courts, including cases raising issues of public international law, and matters relating to arbitration.

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A great advocate with an amazing patience for sifting through the facts.

Chambers UK Bar 2021

A powerful intellect and good to work with.

The Legal 500 UK Bar 2021

Excellent on maritime delimitation and a superstar on state responsibility.

Chambers UK Bar 2021

Very talented and a real star in the making in the field of international law.

The Legal 500 UK Bar 2020

An acknowledged expert on the law of state responsibility.

Chambers UK Bar 2020

He has a strong academic background in PIL and a keen interest in the law of state responsibility.

Chambers and Partners Global Bar 2019

Very thorough, meticulous and provides very good written work.

Chambers UK Bar 2020

He is very bright and has excellent knowledge of international law.

Chambers and Partners Global Bar 2019

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