Courtney has a wide-ranging practice in international, commercial and human rights law, and often acts at the intersection of these areas. She is described as “a real superstar”. She “pairs excellent advice with brilliant instincts and judgment”, is “incredibly thorough and totally reliable”, “a beautiful drafter” who is “a true pleasure to work with”, and an “absolutely brilliant team player”: “you can count on her completely”.
Courtney’s commercial practice includes both litigation and arbitration, and encompasses civil fraud, high-value contract disputes, enforcement proceedings and challenges to awards in London-seated arbitrations, shipping and general commercial disputes. She has acted (led and unled) in cases in the County Court, Commercial Court, King’s Bench Division, Court of Appeal and Supreme Court. She has also appeared before arbitral tribunals under a variety of institutional rules (including UNCITRAL, LMAA, LCIA and ICC). She is a member of the Attorney General’s Civil Panel.
Courtney is also an expert on INTERPOL, which complements her civil fraud practice. She is the co-author of the leading text on INTERPOL, The Legal Foundations of INTERPOL (2nd edition, 2020), advises States on INTERPOL matters, and is well-versed in challenging INTERPOL red notices.
As to her international practice, Courtney has recently acted in cases before the International Court of Justice, the International Tribunal for the Law of the Sea, the European Court of Human Rights and the International Criminal Court. She is also instructed in investor-State proceedings and in domestic cases which raise issues of public international law and foreign relations law, including State immunity and the foreign act of State doctrine. She is a member of the Attorney General’s Public International Law Panel.
The diversity of her practice is exemplified by her recent cases. These include acting on behalf of: Dechert in the English courts in claims arising out of the alleged torture of prisoners in Ras Al Khaimah (Al Sadeq v Dechert); the United Kingdom at the International Tribunal for the Law of the Sea in climate change proceedings (Request for an Advisory Opinion submitted by the Commission of Small Island States on Climate Change and International Law); a P&I insurer in the Court of Appeal, seeking anti-suit relief against Venezuela (UK P&I Club NV v Venezuela); Ukraine at the European Court of Human Rights in proceedings arising out of the Russian invasion (Ukraine v Russia); Greggs plc in the English courts in its claim for over £150 million in business interruption losses (Greggs Plc v Zurich Insurance Plc); and an international athlete at the Court of Arbitration for Sport (UK Anti-Doping v Boardman).
Before joining Twenty Essex, Courtney qualified as a solicitor-advocate and worked at a leading Wall Street firm. Courtney was also a Judicial Assistant at the UK Supreme Court to Lord Hodge and Lord Lloyd-Jones. She is a graduate of Yale University and the University of Cambridge.
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Example cases
- Ukraine v Russia – acting for Ukraine in inter-state proceedings brought by Ukraine against the Russian Federation at the European Court of Human Rights arising out of the Russian Federation’s invasion of Ukraine (team led by Lord Guglielmo Verdirame KC and Tim Otty KC).
- The M/T “Heroic Idun” (No. 2) Case (Marshall Islands/Equatorial Guinea) – representing the Republic of the Marshall Islands in proceedings against Equatorial Guinea at the International Tribunal for the Law of the Sea in respect of its interception, diversion and detention of the “Heroic Idun” and her crew (team led by Sir Daniel Bethlehem KCMG KC).
- Obligations of States in respect of climate change – acting for a State in proceedings before the International Court of Justice concerning the obligations of States under international law to ensure the protection of the environment from anthropogenic emissions of greenhouse gas emissions.
- Greggs plc v Zurich Insurance plc [2022] EWHC 2545 (Comm) – acted for Greggs plc in its claim for over £150 million in business interruption losses arising during the COVID-19 pandemic (with Christopher Hancock KC and Simon Milnes KC).
- Acting on behalf of politically exposed persons at the Commission for the Control of INTERPOL’s Files to seek the deletion of notices and diffusions.
- Maxis Communications Berhad and Global Communication Services Holdings Limited v. Republic of India – acting for two investors in proceedings under bilateral investment treaties concerning India’s breaches of duties in the telecommunications sector (led by Toby Landau KC and Lucas Bastin KC, UNCITRAL Rules).
- RCGS “Resolute” [2023] EWCA Civ 1497 – acting on behalf of the P&I insurer at the court of Appeal seeking an anti-suit injunction against the Republic of Venezuela to restrain it from pursuing foreign proceedings on the basis that the infringement of Article 6(1) of the European Convention on Human Rights by the statutory prohibition on (anti-suit) injunctive relief in section 13(2)(a) of the State Immunity Act 1978 cannot be justified, by reference to customary international law or domestic public policy, as pursuing a legitimate objective by proportionate means (with David Lewis KC and Alexander Thompson).
- UK Anti-Doping Limited v Boardman – acting for an international athlete at the Court of Arbitration for Sport in an appeal of the decision of the National Anti-Doping Panel not to impose a period of ineligibility for the athlete’s anti-doping rule violation (with Luke Pearce KC).
- Advising the UK Foreign, Commonwealth and Development Office on issues of public international law.
- Advising the UK Government on the defensibility of sanctions related to individuals in the Russian Federation, Belarus, Eritrea and Venezuela.
Arbitration
- Maxis Communications Berhad and Global Communication Services Holdings Limited v. Republic of India – acting for two investors in proceedings under bilateral investment treaties concerning India’s breaches of duties in the telecommunications sector (led by Toby Landau KC and Lucas Bastin KC, UNCITRAL Rules).
- Advising an American luxury automotive supplier on a dispute relating to breach of a sale and purchase agreement relating to earn-out provisions.
- Acted for a flag State in Annex VII proceedings under the UN Convention on the Law of the Sea.
- UK Anti-Doping Limited v Boardman – acting for an international athlete at the Court of Arbitration for Sport in an appeal of the decision of the National Anti-Doping Panel not to impose a period of ineligibility for the athlete’s anti-doping rule violation (with Luke Pearce KC).
- Acted as sole counsel in an ad hoc arbitration.
- Assisted in a multi-billion dollar private equity fraud dispute (with Charles Kimmins KC).
- Assisted in defending a challenge brought under section 68 of the Arbitration Act 1996 in respect of an arbitration award (with Luke Pearce KC).
- Assisted in an arbitration conducted in accordance with the LMAA Small Claims Procedure 2017 (with Luke Pearce KC).
- Drafted pleadings in an LMAA arbitration on the frustration of a charterparty as a result of COVID-19.
Commercial litigation
- Al Sadeq and Quzmar v Dechert and others – acting in high-profile claims arising out of alleged misconduct by solicitors in connection with a foreign fraud investigation.
- Greggs plc v Zurich Insurance plc – acted for Greggs plc in its claim for over £150 million in business interruption losses arising during the COVID-19 pandemic (with Christopher Hancock KC and Simon Milnes KC).
- In the matter of an Impressionist Painting –[2020-23] (Ch.D) – acted for the American owner of a high value impressionist painting by Paul Signac, which was taken from her in New York under false pretences by a fraudulent art dealer before being sold on the London art market through the second defendant art gallery to an English art collector (with Paul Lowenstein KC and Susannah Jones).
- Durnont Enterprises v BNP Paribas Bank Polska SA and others – acted for a foreign company in a £100 million derivative claim (team led by Philip Riches KC).
- Acted for a U.S. investment bank in connection with criminal investigations in relation to the hiring of family members of high-ranking foreign officials in China.
- Assisted in a hacking dispute in which persons unknown gained access to cryptocurrency accounts and conducted a series of fraudulent trades (with Josephine Davies).
- Vedanta Resources plc v Lungowe and others [2019] UKSC 20, [2020] AC 1045 (landmark case on jurisdiction and parent company liability) – appeal concerned claims brought by 1,826 Zambian citizens who allege that they have suffered damage as a result of toxic discharges from one of the world’s largest copper mines (as a Judicial Assistant). Court held there was an arguable case that the UK parent company owed a duty of care to third parties affected by its Nigerian subsidiary.
Human rights, sanctions and public law
- Ukraine v Russia – acting for Ukraine in inter-state proceedings brought by Ukraine against the Russian Federation at the European Court of Human Rights arising out of the Russian Federation’s invasion of Ukraine (team led by Lord Guglielmo Verdirame KC and Tim Otty KC).
- Al Sadeq and Quzmar v Dechert and others – acting in high-profile claims arising out of alleged torture and misconduct said to have been carried out in connection with a foreign fraud investigation.
- Hedges and another v State officials of the United Arab Emirates [2019-2024] (KBD) – case concerning whether the immunity of State officials in the context of allegations of torture violates Article 6 of the European Convention on Human Rights (team led by Sir Daniel Bethlehem KCMG KC).
- The British Council v Mrs Ana-Maria Beldica [2024] EAT 92 – advised on issues of human rights and public international law in an appeal to the Employment Appeal Tribunal. The case concerned (inter alia) whether the act of claiming State and/or diplomatic immunity in foreign proceedings is sufficient to justify a finding that the UK was exercising jurisdiction extraterritorially for the purposes of Article 1 of the ECHR.
- RCGS “Resolute” – acting on behalf of the P&I insurer seeking an anti-suit injunction against the Republic of Venezuela to restrain it from pursuing foreign proceedings on the basis that the infringement of Article 6(1) of the European Convention on Human Rights by the statutory prohibition on (anti-suit) injunctive relief in section 13(2)(a) of the State Immunity Act 1978 cannot be justified, by reference to customary international law or domestic public policy, as pursuing a legitimate objective by proportionate means (with David Lewis KC and Alexander Thompson).
- R (on the application of Al Haq) v Secretary of State for Business and Trade [2025] EWHC 173 (Admin) – acting for Al Haq in judicial review proceedings to challenge the decision of the UK Government to exclude F-35 fighter jet parts from its suspension on the export of arms to Israel. This case featured as one of the Top 20 cases of 2025 in The Lawyer.
- Advising a State in relation to the African Charter on Human and Peoples’ Rights.
- Advising on the designation of managers of various vessels under the Russia (Sanctions) (EU Exit) Regulations 2019.
- Advised on the designation of an Eritrean military group under the Global Human Rights Sanctions Regulations 2020.
- Advised on the designation of various Russian politicians under the Russia (Sanctions) (EU Exit) Regulations 2019.
- Advised on the designation of individuals from Belarus under the Republic of Belarus (Sanctions) (EU Exit) Regulations 2019.
- Advised on the designation of politicians from Venezuela under the Venezuela (Sanctions) (EU Exit) Regulations 2019.
- Advised the Public International Law & Policy Group on State reparation programmes and post conflict compensation laws to provide precedents for legal reform of the 2009 National Compensation Law in Iraq for victims of terrorism.
- Elgizouli v Secretary of State for the Home Department [2020] UKSC 10, [2021] AC 937 – assisted on a case concerning whether it is lawful for the Secretary of State to engage in mutual legal assistance that will facilitate the imposition of the death penalty in another State (as a Judicial Assistant).
INTERPOL
- Acting on behalf of politically exposed persons at the Commission for the Control of INTERPOL’s Files to seek the deletion of notices and diffusions.
- Advised on membership in INTERPOL and the suspension of members from access to the INTERPOL Information System. Advised on the privileges and immunities of INTERPOL, and the privileges and immunities of INTERPOL officials.
- Co-authored the leading text on INTERPOL, The Legal Foundations of INTERPOL (2nd edn, Hart Publishing, 2020).
Public international law
International courts and tribunals
- Obligations of States in respect of climate change – acting for a State in proceedings before the International Court of Justice concerning the obligations of States under international law to ensure the protection of the environment from anthropogenic emissions of greenhouse gas emissions.
- The M/T “Heroic Idun” (No. 2) Case (Marshall Islands/Equatorial Guinea) – representing the Republic of the Marshall Islands in proceedings against Equatorial Guinea at the International Tribunal for the Law of the Sea in respect of its interception, diversion and detention of the “Heroic Idun” and her crew (team led by Sir Daniel Bethlehem KCMG KC).
- Right to Strike under ILO Convention No. 87 – acting for a State in proceedings before the International Court of Justice on the issue of whether the right to strike of workers and their organizations is protected under the Freedom of Association and Protection of the Right to Organise Convention, 1948 (No. 87).
- Ukraine v Russia – acting for Ukraine in inter-state proceedings brought by Ukraine against the Russian Federation at the European Court of Human Rights arising out of the Russian Federation’s invasion of Ukraine (team led by Lord Guglielmo Verdirame KC and Tim Otty KC).
- Obligations of Israel in relation to the Presence and Activities of the United Nations, Other International Organizations and Third States in and in relation to the Occupied Palestinian Territory – acting for Pakistan at the International Court of Justice in advisory proceedings concerning the obligations of Israel, including to ensure the provision of essential supplies, basic services and humanitarian and development assistance for the benefit of the Palestinian civilian population.
- Request for an Advisory Opinion submitted by the Commission of Small Island States on Climate Change and International Law – acted on behalf of the United Kingdom at the International Tribunal for the Law of the Sea in advisory proceedings concerning States Parties’ obligations in relation to climate change and ocean acidification (with Ben Juratowitch KC, Amy Sander and Belinda McRae).
- Maxis Communications Berhad and Global Communication Services Holdings Limited v. Republic of India – acting for two investors in proceedings under bilateral investment treaties concerning India’s breaches of duties in the telecommunications sector (led by Toby Landau KC and Lucas Bastin KC, UNCITRAL Rules).
- The M/T “Heroic Idun” Case (Marshall Islands v. Equatorial Guinea), Prompt Release – represented the Republic of the Marshall Islands in prompt release proceedings against Equatorial Guinea at the International Tribunal for the Law of the Sea in respect of the “Heroic Idun” (application was withdrawn when the vessel was transferred to the Republic of Nigeria).
- Acted for a flag State in Annex VII proceedings under the UN Convention on the Law of the Sea.
International law in domestic courts
- Hedges and another v State officials of the United Arab Emirates [2019-2024] (KBD) – case concerning the immunity of State officials in the context of allegations of torture (team led by Sir Daniel Bethlehem KCMG KC).
- The British Council v Mrs Ana-Maria Beldica [2024] EAT 92 – advised on issues of State immunity, diplomatic and consular immunity, and customary international law in an appeal to the Employment Appeal Tribunal. The case concerned (inter alia) whether the act of claiming State and/or diplomatic immunity in foreign proceedings is sufficient to justify a finding that the UK was exercising jurisdiction extraterritorially for the purposes of Article 1 of the ECHR.
- RCGS “Resolute” [2023] EWCA Civ 1497 – acting on behalf of the P&I insurer seeking an anti-suit injunction against the Republic of Venezuela to restrain it from pursuing foreign proceedings on the basis that the infringement of Article 6(1) of the European Convention on Human Rights by the statutory prohibition on injunctive relief in section 13(2)(a) of the State Immunity Act 1978 cannot be justified, by reference to customary international law or domestic public policy, as pursuing a legitimate objective by proportionate means (with David Lewis KC and Alexander Thompson).
- R (on the application of Al Haq) v Secretary of State for Business and Trade [2025] EWHC 173 (Admin) – acting for Al Haq in judicial review proceedings to challenge the decision of the UK Government to exclude F-35 fighter jet parts from its suspension on the export of arms to Israel. This case featured as one of the Top 20 cases of 2025 in The Lawyer.
- Assisted on a case concerning the proper interpretation of Article 39(1)-(2) of the 1961 Vienna Convention on Diplomatic Relations (VCDR) on the commencement and termination of privileges and immunities.
- Assisted on a case concerning the appointment of members of staff of the mission under Article 7 of the VCDR, notification to the host State under Article 10 of the VCDR, a declaration that a diplomat is persona non grata under Article 9 of the VCDR, and how to obtain a certificate under s 4 of the Diplomatic Privileges Act 1964 from the Foreign, Commonwealth & Development Office.
- Assisted on a case concerning the extent to which the Consular Relations Act 1968 gives effect in domestic law to the 1963 Vienna Convention on Consular Relations (VCCR), whether Article 36 of the VCCR (communication and contact with nationals of the sending State) reflects customary international law, and the proper interpretation of Article 36 of the VCCR.
- R v Reeves Taylor (Agnes) [2019] UKSC 51, [2021] AC 349 – assisted on a case concerning the proper interpretation of “acting in an official capacity” in the UN Convention Against Torture and s 134 of the Criminal Justice Act 1988 (as a Judicial Assistant).
Advisory
- Advising a State in relation to a claim under the Convention on the Prevention and Punishment of the Crime of Genocide, and the International Convention on the Elimination of All Forms of Racial Discrimination.
- Advising a State in relation to a preliminary investigation at the International Criminal Court.
- Advised an NGO on a claim under the 1951 Refugee Convention, and the OAU Convention Governing the Specific Aspects of Refugee Problems in Africa.
- Advised on issues relating to the Chagos Islands.
- Advised a State whose Minister had been detained by the UK National Crime Agency on the immunity and inviolability of State property.
- Advised the UK Government on the privileges and immunities of international organisations and their officials (as a matter of domestic law and international law).
- Revised guidance on the privileges and immunities of diplomats and consuls for use by UK police forces.
- Advised the UK Government on the implications of dual nationality on the privileges and immunities of a British ambassador and his family under the VCDR and the VCCR.
- Advising on employment law issues relating to the termination of a diplomat’s functions.
- Advised the UK Government on urgent issues of diplomatic and consular protection, and the privileges and immunities of diplomats and consuls, often on an emergency basis, in the context of the COVID-19 pandemic.
- Advised the UK Government on treaty interpretation in the context of issues concerning the 2020 Agreement on the Withdrawal of the UK from the EU (team led by Lord Guglielmo Verdirame KC).
- Advised the Public International Law & Policy Group on State reparation programmes and post conflict compensation laws to provide precedents for legal reform of the 2009 National Compensation Law in Iraq for victims of terrorism.
Courtney was seconded to the UK Foreign and Commonwealth Office in 2020 where she worked as an Assistant Legal Adviser.
