Lionel Nichols and Emile Simpson Appointed to Attorney General’s Public International Law Panel
Four New Square Chambers are delighted to announce the appointment of two…
Lionel Nichols is a leading junior specialising in international and cross-border disputes, with a practice spanning commercial litigation, international arbitration and public international law. He is regularly instructed in high-value, complex matters, acting for States, corporations and individuals before the English courts and a wide range of international tribunals.
Lionel initially qualified as a solicitor in Australia in 2008, practising in commercial litigation, before transferring to the English Bar in 2013.
Lionel graduated with a triple first (Law, Politics, and Philosophy) and a Master of International Politics from the University of Tasmania before being awarded a Rhodes scholarship to study at the University of Oxford where he graduated with a Bachelor of Civil Law, a Master of International Politics and a Doctor of Philosophy in Law.
Lionel also sits as an arbitrator and is a Fellow of the Chartered Institute of Arbitrators.
A selection of Lionel’s experience is provided below. More comprehensive information is available on request.
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Lionel practises in commercial dispute resolution, with a focus on High Court litigation involving complex, international and multi-jurisdictional disputes. He has experience acting in disputes across a range of areas, including finance, civil fraud and general commercial matters, including:
He is instructed both as sole counsel and as part of larger teams, and is experienced in managing complex litigation from early-stage applications through to trial.
Featured Commercial Law Cases
Lionel has a broad international arbitration practice encompassing complex, high-value commercial disputes across multiple sectors, including financial services, energy, insurance, shipping and civil fraud. His work frequently involves cross-border disputes with parallel proceedings, and he is experienced in acting both as part of counsel teams and as sole counsel.
He is regularly instructed in arbitrations seated in major arbitral centres worldwide, including proceedings under the CIArb, HKIAC, ICC, ICSID, LCIA, SCC, SIAC and UNCITRAL Rules, as well as ad hoc arbitrations. The sectors covered by this practice include banking & financial services, commodities and international trade, and energy & infrastructure, with a focus on Africa, CIS & Russia, as well as offshore jurisdictions. He has also advised both claimants and States in relation to potential claims under bilateral and multilateral investment treaties.
His experience spans the full lifecycle of disputes, from pre-arbitration strategy and pleadings through to evidential hearings and post-award challenges and enforcement. He has acted for a diverse client base including multinational corporations, financial institutions and high-net-worth individuals, and is accustomed to working on large-scale disputes involving complex factual and legal issues.
Alongside his arbitration practice, he has significant experience of arbitration-related litigation before the English courts, including challenges to awards, applications for interim relief and enforcement proceedings. He has particular expertise in applications under the Arbitration Act 1996, including challenges under sections 67, 68 and 69, stays of proceedings under section 9, freezing injunctions under section 44 and determinations of jurisdiction under section 32.
Lionel also sits as an arbitrator and is a Fellow of the Chartered Institute of Arbitrators.
Featured International Arbitrations as Counsel
Arbitration Experience
Court-Related Arbitration Experience
Featured Arbitral Appointments
Lionel has sat as arbitrator in over a dozen arbitrations and has experience both as sole arbitrator and as part of a panel. He has more than 15 years of experience in international arbitrations, including proceedings under the CIArb, HKIAC, ICC, ICSID, LCIA, SCC, SIAC and UNCITRAL Rules, as well as ad hoc arbitration. He is a Fellow of the Chartered Institute of Arbitrators and a member of the London Court of International Arbitration.
Recent experience includes:
Lionel is one of London’s most experienced juniors in public international law. His broad practice includes advising individuals, NGOs and States on all aspects of public international law, including:
On 1 January 2026, Lionel was appointed to the Attorney General’s ‘B’ Panel for Public International Law and is currently serving a five-year term.
Lionel’s experience includes acting as Geoffrey Robertson KC’s first-choice junior on all aspects of public international law. In addition to casework, Lionel provided research assistance on numerous academic titles, including Crimes against Humanity, The Case of the Pope, An Inconvenient Genocide, Mullahs Without Mercy and Who Owns History?
He holds two master’s degrees in international law, a master’s degree in international relations, and a doctorate in international law which was examined by Professor Dapo Akande. Prior to joining Chambers, Lionel was the Global Justice Research Fellow at the University of Oxford. He has published widely in the field of public international law and is regularly invited to speak at conferences. He is the author of The International Criminal Court and the End of Impunity in Kenya.
Lionel is currently advising the Norfolk Island Government in its attempts to obtain the status of non-self-governing territory under Chapter XI of the United Nations Charter.
Featured Public International Law Cases
International Court of Justice
United Nations Human Rights Committee
International Criminal Law
European Court of Human Rights
African Commission on Human and Peoples’ Rights
Investment Treaty Arbitrations
Domestic Courts
Lionel’s extensive experience and expertise in commercial litigation, human rights, public international law and private international law have him uniquely placed to act on ESG, business & human rights and climate change matters. He has experience in matters involving:
Lionel’s recent experience includes:
Lionel’s recent ESG publications include:
Lionel has also served as an expert reviewer in a comparative study conducted by the University of Oxford’s Bonavero Institute of Human Rights on civil liability for human rights violations across 18 jurisdictions.
Lionel is regularly asked to advise on sanctions issues. He has experience in advising clients on all aspects of sanctions law across the UN, EU and UK frameworks, particularly in the context of financial sanctions and export control. He also advises clients in relation to potential sanctions challenges.
Recent experience includes:
Lionel advises and acts for various stakeholders in litigation relating to all forms of the law and practice of insolvency and is regularly instructed to appear in the Insolvency & Companies Court.
He has experience acting for and advising companies, private individuals, partnerships, LLPs and insolvency practitioners on all aspects of corporate and personal insolvency including administration, bankruptcy, liquidation, winding-up petitions and applications to set aside statutory demands. Reflecting his broader practice, Lionel is particularly sought after for cases with an international or offshore dimension.
He is also regularly involved in shareholder disputes, unfair prejudice petitions, derivative claims, litigation arising out of corporate transactions and matters involving corporate governance and directors’ duties.
Recent experience includes:
Lionel is regularly instructed in jurisdiction challenges in both the English courts and in international arbitration.
Within litigation, Lionel has experience in dealing with matters involving the Brussels I Regulation (and the associated Brussels and Lugano Conventions) on jurisdiction and enforcement of judgments, challenges on forum non conveniens grounds, and Rome I and Rome II regulations on the law application to contracts and to non-contractual obligations.
In international arbitration, Lionel is an expert in jurisdictional challenges both before arbitral tribunals but also under sections 9, 32, and 67 of the Arbitration Act.
Recent experience includes:
Legal 500“His quick understanding and appreciation, thoughtful questions, careful explanations, clever and clear drafting, and collaborative approach to the development of case strategy are impressive.”
Legal 500
Commercial Litigation
Fellow of the Chartered Institute of Arbitrators
DPhil in Law (University of Oxford)
MPhil in Law (Dist.) (University of Oxford)
BCL (University of Oxford)
Master of International Politics (University of Tasmania)
Bachelor of Laws (1st) (University of Tasmania)
Bachelor of Arts (1st) (University of Tasmania)
Rhodes Scholarship, Commonwealth Scholarship, Tim Hawkins Memorial Scholarship
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