JUNIOR PROFILE

Simon Olleson

UK Bar 2026

Twenty Essex

Ranked in 1 practice area

Public International Law

London (Bar)

19 years ranked

About

Provided by Twenty Essex

Practice Areas

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).

Career

Read a full summary of Simon's career on the Twenty Essex website

Chambers Review

Provided by Chambers

UK Bar

Public International Law - London (Bar)

Band 1

Individual Editorial

Simon Olleson has a strong academic background in PIL and a keen interest in the law of state responsibility. He has recently advised on the PIL angles of environmental disputes and shown himself to be an expert in maritime delimitation cases and BIT arbitration. He has acted in ICJ, PCA, ICSID and ad hoc arbitration proceedings.

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Strengths

Provided by Chambers

Simon is a go-to for me in the heavy research-focused cases.
Public International LawUK Bar
Simon is really clever; his forensic analysis and mastery of the law is evident. He produces excellent advocacy, both written and oral.
Public International LawUK Bar