Hugh Mercer KC

Professional practice

Hugh Mercer KC is a very experienced advocate with extensive experience at appellate level in England and Wales (more than ten Supreme Court/House of Lords cases), in the CJEU and before the courts of other countries (including Switzerland, Guyana and Cyprus) working as part of a team with local counsel. His practice has two broad strands covering both public law and private law.

The first is challenges against states and the actions of state entities. This encompasses: public & regulatory law (e.g. competitition, sanctions and any activity regulated by public law); Brexit (including NI Protocol); human rights; public international and investment law, including for example acting for the UK as lead advocate in its dispute with the EU under the Trade and Cooperation Agreement over British access to EU science programmes (Horizon & Euratom).

The second strand is international commercial litigation with an emphasis on jurisdictional challenges and private international law, foreign law in the English courts and international arbitration such as an arbitration over the impact of Greek/Italian law of good faith on contractual payment obligations before an LCIA arbitral tribunal.

In the legal directories he is described by clients as “masterful on his feet” with “an incredible ability to distil complex legal arguments into pithy points”, “A super lawyer,” “a creative thinker”, “He has the finest mind I have encountered.” He chairs the International Committee of the Bar of England and Wales and the Delegation of the UK Bars and Law Societies to the CCBE.

He sits as a Deputy High Court Judge and as an arbitrator/mediator. He is a Master of the Bench of Middle Temple. He has excellent French, good German, Spanish and Italian. He also practises in Northern Ireland and in Brussels, as a Belgian avocat with a right to plead in the CJEU.

What Others Say

Chambers and Partners UK 2025

“His knowledge of EU law is impressive and his advice on the strategy of intervention is strong.”

“He is very well prepared, competent and assured.”

“Hugh is a careful and considered advocate who combines intellect with courage and attractive advocacy.”

“He is extremely academic as well as being fantastic on his feet.”

“Hugh Mercer is at the top of his game in terms of his grasp of the detail regarding agricultural policy.”

“Hugh is articulate, excellent in terms of developing and considering complicated matters and has an understanding or and expertise in agriculture.”

“Hugh Mercer KC has excellent institutional knowledge of the EU and is a real team player.”

“Hugh Mercer KC is very responsive and turns work around to tight deadlines.”

“Hugh Mercer KC has an unrivalled ability to take up new areas of law in ever-changing times and is a leading light in the field in European law.“

Legal 500 2025

“Hugh combines an excellent mind with a superb grasp of the facts.”

“Hugh has excellent qualities in conference and is tenacious and able in court. He has a high level of knowledge of agriculture.”

“Hugh’s knowledge of EU law and procedure is encyclopaedic. His experience and expertise shines through in all of the advice that he gives – getting to an answer in 30 seconds that takes the rest of us days to reach.”

Chambers and Partners UK 2024

“Hugh produces very well-drafted advice and provides good service levels, well combined with an academic approach.”

“Both clients and I were very happy with his advice and the presentation of the case to the court.”

Chambers and Partners UK 2023

“Hugh Mercer KC is exceptional. He is a brilliant advocate and has an incredibly ability to distil complex legal arguments into pithy points.”

“He provides very good analysis and excellent advocacy.”

“He is always a very impressive advocate.”

“He provides very good analysis and excellent advocacy.”

“Hugh Mercer KC is exceptional. He is a brilliant advocate and has an incredibly ability to distil complex legal arguments into pithy points.”

Legal 500 2023

“He has the finest mind I have encountered on administrative law issues relating to food and agriculture and EU law generally.”

Legal 500 2022

“He has the finest mind I have encountered on administrative law issues relating to food and agriculture and EU law generally.”

“He has a very impressive ability to break down and present complex legal arguments in a readily understandable and persuasive way.”

Chambers and Partners UK 2022

“He is a creative thinker who brings new ideas and is constantly innovating rather than simply reproducing case law.”

“He is a unique and special advocate with unrivalled expertise in EU Agricultural law.”

“A terrific EU and English constitutional lawyer.”

Legal 500 2021

“A masterclass in terms of his ability to assimilate complex issues.”

“An excellent advocate able to distil complex legal arguments in a manner accessible to the court.”

“He is undoubtedly extremely strong on all relevant jurisdictional conflict issues.”

Chambers and Partners UK 2020

“He is masterful on his feet. His preparation is so immaculate and tells the story in such a way that it is easy to follow. It sort of spoils you because you can’t instruct him on everything.”

Legal 500 2020

“A leading light in agricultural and public law issues… He shows in-depth knowledge of EU civil procedure law and creativity to find out-of-box solutions.” A creative and industrious lawyer, his preparation is meticulous and well judged.”

Chambers and Partners UK 2019

“He has a very good way of building arguments in a straightforward and convincing way, an ability to look at questions from different angles and an enormous knowledge of EU law… Knows European law back to front and works very closely with us in ensuring that our client’s needs are met.”

Regulatory Law

A specialist practitioner in the conduct of regulatory proceedings/investigations spanning a range of sectors including environment, telecoms, water, gas, travel, shipping and health. Has particular experience in the application of human rights to regulatory proceedings. Practises in the UK and the EU and can handle any subsequent public law proceedings in the Administrative Court or the General Court of the EU. See also Energy and Environmental Regulation and Group Actions below.

Re Legacy of Northern Ireland Troubles Proposals, (proposed amnesty for persons accused of Troubles crimes and termination of civil proceedings & inquests – human rights – duty to investigate unexplained deaths – legality of proposals to address legacy to the Troubles)
Thomas v Guyana, (whether incompatibility between constitutional right to a healthy environment and prior grant of a petroleum extraction licence)
Unwired Planet v. Huawei Supreme Court (representing Apple Inc in a challenge on grounds of breach of international law to English court effectively fixing royalty rate for US consumers on US patents in USA)
Bayer v. European Commission, CJEU, (whether European Commission prohibition of pesticide infringed procedural protection under the terms of the authorization)
Hemming v. Westminster City Council, Supreme Court (costs and fees repayable by a regulator in the event that it has been operating an unlawful schedule of fees)
Bruce Baker v. Boxing Board of Control, (boxing promoter involved in two promotions regulated by German Boxing Association – whether restriction in rules of British Board of Control lawful – injunction)
Bloomsbury v. Sea Fish Authority Supreme Court, Supreme Court (interpretation of statutory power of public authority to impose levy on sea fish and compatibility with EU law of charges)
Repertoire Culinaire v. HMRC CJEU (correct classification for the purposes of excise duty of cooking wine to which salt & pepper had been added)
R (Intertanko) Secretary of State for Transport, CJEU, (MARPOL Treaty – whether the EU Ship Source Pollution Directive breached the public international law obligations of the EU)
Boake Allen v. HMRC, House of Lords (double taxation conventions – whether availability of group income elections breached conventions)
R v. West Somerset Coroner ex p Middleton, House of Lords (human rights – inquests – statutory provisions for the verdict of inquests must be interpreted as requiring a verdict as to the means by which a person died but also the circumstances in which they died)
Stevenage v. Football League, Court of Appeal (promotion to football league – membership criteria fulfilled – delay beyond end of season – application for injunctive relief rejected on grounds of delay)

Competition Law

Very experienced in the conduct of regulatory investigations in the utilities, food, agriculture and telecoms sectors both in the UK and the EU.

Advice to local authority in relation to application of Subsidy Control Act 2022 (long-standing project of urban regeneration – transition between state aid regime via Trade and Cooperation Agreement to Subsidy Control Act 2022)
Vtesse Harlow Ltd v. European Commission, CJEU (challenge to decision of European Commission to close a state aid investigation in respect of a competitor)
Arla v. Stellantis (formerly Fiat Chrysler) Competition Appeal Tribunal (pending claim arising from trucks cartel – claim for losses suffered in multiple jurisdictions)
Microsoft v. Commission CJEU, (Microsoft fined for failure to make available on fair, reasonable and non-discriminatory terms windows for workgroups software – mandatory order by to make it available on FRAND terms – lack of certainty as to what Commission considered to be FRAND terms – refusal by Commission to provide guidance as to meaning of the Order)
Arbitration on effect of EC competition law on specialist shipping pool (common agreements voluntarily entered into between all members of a specialist shipping pool – whether agreements contrary to Article 101 TFEU and/or Chapter 1 and unlawful)
Thai Airways v. BA (claim arising from air cargo cartel – fixing of prices and other conditions for airfreight)
Arkin Borchard Lines Commercial Court (liner shipping agreement – independent shipper complained of anti-competitive activity by the conference – allegations of abuse of dominant position – rejected)
European Commission v. East Africa Conference Lines (allegations of anti-competitive activity and abuse of a dominant position on liner shipping route from Europe to East Africa – challenge to European Commission
Lidl v Swale BC & Aldi Administrative Court (sale by Council of land to one supermarket – whether breach of local government legislation – whether unlawful state aid)

Energy & Environmental Regulation

Covers a range of environmental issues arising in farming and fisheries contexts such as the application of the precautionary principle to the ecosystem of the mid-Atlantic ridge but is also involved in judicial review of secondary legislation in the field of the environment.

Has had regular involvement with climate change issues, both under EU and UK law, including both the CRC Trading Scheme and the EU Emissions Trading System.

Has been involved in most of the big regulatory issues between food and farming interests and public authorities over the last 15-20 years, often but not exclusively with an EU flavour. He has litigated many issues on definition of food products, pesticide authorisation and issues of Single Payment or Basic Payment Scheme including alleged cross-compliance breaches.

R (NFU) v. Welsh Government Administrative Court (Welsh Government policy to protect land from nitrates – increase from 2.4% of land area to 100% – whether failure to have regard to an essential consideration, cost of compliance)
Bayer v. European Commission CJEU, (ban of authorised pesticide – whether failure to take account of acquired right – whether new science needed to review approval – failure to obtain comprehensive risk assessment)
King v. Environment Agency, High Court (Agency used farmland as water storage area for water to protect city – up to four months per annum – whether Article 1 Protocol 1 ECHR required compensation for use of land)
R (Mabanaft) v. Secretary of State for Energy and Climate Change Court of Appeal (compulsory petroleum stocks – differential regulation for refiners and importers – challenge to distribution of the charges and differences in volume of stock)
Poland v. European Commission CJEU (challenge to Member State action plan in relation to application of EU emissions trading scheme – acted for UK in support of European Commission)

Group Actions

Has been involved in litigation involving multiple damages claims arising from actions of both Governments and of private companies in the field of insurance, financial services, tax and also in both stand alone and follow-on actions for damages arising from cartels for example in the vitamins cartel and the air cargo cartel. See also Competition, above.

Municipio de Mariana v BHP Group High Court (collapse of Fundão Dam, Brazil – suit against UK parent company – 200,000 claimants – whether refusal of permission to appeal against striking out unlawful)
Re EU & International law, Federal Court of Australia, (expert witness on EU and International law in group litigation arising out of diesel emissions claims
AMT Futures Limited v. Marzillier Supreme Court (challenge to English jurisdiction; derivatives trader sued German law firm in London for allegedly inducing hundreds of German consumer investors to sue trader in German courts in breach of English jurisdiction clause; damage occurred on commencement of proceedings by consumers in Germany)
Czakja and others v. Volkswagen AG, Court of Appeal, Poland (Diesel emissions – liability of contracting car dealerships – jurisdiction over proceedings against manufacturer
Group of investors v Gain Capital Commercial Court (Claim for repayment of sums advanced by hundreds of investors in Ponzi scheme – interpretation of regulatory provisions – measure of restitutionary claim)
Poole v HM Treasury Court of Appeal (alleged failure correctly to implement EU insurance directives – group of Lloyd’s Names – whether entitled to damages for failure to implement.

Sanctions

Qualified to advise on both UK and EU sanctions. Has provided advice and representation in court in relation to most EU and UK sanctions regimes directed against Russia, Iran, China, Myanmar, Syria, Libya, Egypt, Zimbabwe, both for listed parties and for those persons alleged to be associated with and/or owned/controlled by the listed party. Also experienced in relation to secondary sanctions and use of the blocking statutes.

Tecnimont v LLC Eurochem North-West-2, Commercial Court, 2023, (alleged breach of anti-suit injunction by participation in foreign regulatory proceedings to support a decision determining that ECM’s assets were frozen under EU sanctions through ownership/control)
Arbitration in relation to US sanctions on Iranian companies (Iranian state entity contracted with German specialist repairer – US sanctions introduced against Iranian entity – German business also having US interests – German business claiming to avoid contract – Iranian entity pleading EU Blocking Regulation)
Advice to Russian founded EU business (restructured in 2014 – former owner listed in 2022 – whether owned and controlled by listed person)
Huawei v. Libya Investment Authority, District Court of Port Louis, Mauritius (whether EU Libya sanctions rendered the payment for services rendered unlawful; territorial scope under international law of EU sanctions)
Georgias v. European Council CJEU (whether EU sanctions had been lawfully applied to the claimant and whether, if not, claimant was entitled to damages for breach of his fundamental rights)

Public & Administrative Law

Regularly litigates for and against Government entities in England & Wales, Northern Ireland and in Court of Justice of the EU in Luxembourg. Particularly experienced in the application of public law applied to agriculture, fisheries, food, environmental issues and also in relation to a diverse range of regulatory panels and procedures.

In the matter of FM v. Secretary of State for the Home Department, Judicial Review Court, Belfast (illegal entry in 1970s – SSHD aware of circumstances but decided to take no action in 1999 – whether SSHD could revisit 1999 decision)
R (Newby Foods) v. Food Standards Agency, Supreme Court (definition of meat – application of existing definition to new process not existing at time of legislation – environmental costs of restrictive definition – whether admitted skeletal muscle no longer meat through manner of removal from bone)
Hemming v. Westminster City Council, Supreme Court (costs and fees repayable by a regulator in the event that it has been operating an unlawful schedule of fees)
R (Jaspers of Treburley) v. Food Standards Agency, Administrative Court (regulatory charges imposed on meat industry pursuant to EU obligation had been imposed unlawfully as no charging provision in English law which authorised the demand for charges)
R (Friends of the Earth) v. Defra and NFU, Administrative Court (application by NFU for emergency authorisation to use pesticide – decision challenged by environmental group – whether threshold conditions could reasonably be considered to have been satisfied)

Private International Law & Foreign Law

Frequently instructed to handle the specialist conflict of laws issues such as applicable law, service, jurisdiction, taking of evidence etc at the outset of cases. Is an authority on private international in the light of his comparative law commentary (Layton & Mercer, European Civil Practice) on EU private international law. Particularly experienced in cases with expert evidence of foreign law.

Khalifeh v. Blom Bank SAL (consumer jurisdiction under English law for domicile of consumer – whether breach of anti-suit injunction)
Re EU & International law, Federal Court of Australia, (expert witness on EU and International law in group litigation arising out of diesel emissions claims
AMT Futures Limited v. Marzillier Supreme Court (challenge to English jurisdiction; derivatives trader sued German law firm in London for allegedly inducing German consumer investors to sue trader in German courts in breach of English jurisdiction clause; damage occurred on commencement of proceedings by consumers in Germany)
Moreno v. Motor Insurers Bureau Supreme Court (law applicable to tort claims for accidents abroad involving uninsured drivers; claim against MIB in UK but law of place of tort, not English law, applied – overturning CA case law).
Re D Supreme Court (jurisdiction of Supreme Court to entertain appeal; recognition of Romanian child custody order; Brussels II Regulation)
Lehman Brothers Finance AG v. Klaus Tschira Stiftung GmbH, Swiss Supreme Court (true interpretation of jurisdiction clause in ISDA Master Agreement; whether clause providing for exclusive or non-exclusive jurisdiction)
Cox v. Ergo Versicherung AG Supreme Court (whether territorial limitation on English tort statute; whether applicable law was German law as place of accident)
Agnew v. Lansforsakringsbolagens House of Lords (pre-contractual duty of disclosure in relation to insurance contracts – whether tortious or contractual duty for the purposes of rules on jurisdiction)

Public International Law

Leading in various PIL cases, in particular those involving the EU. Experienced advocate in PIL matters including the Law of the Sea, sanctions/restrictive measures, WTO and sovereign debt issues. Advised Greek and Cypriot interests on the legal issues arising from the eurozone crisis and the legality of the actions of the Troika (IMF, European Central Bank, European Commission).

United Kingdom v. European Union (dispute with EU over failure to respect the terms of the TCA re UK joining EU science research programmes, Horizon, Euratom, Copernicus
Re Northern Irish Protocol (advice and representation on interpretation and application of the NI Protocol of the UK-EU Withdrawal Agreement to various sectors and courts
Government of X v. shipping co (Law of the Sea – human rights – collision leading of loss of naval destroyer – co-counsel in courts of State X for shipping company)
United Kingdom v. European Commission (dispute with EU over UK obligations to EU post Brexit & rights to UK representation in CJEU under UK-EU Withdrawal Agreement)
Advice regarding nuclear treaties (advising a government on rights and obligations in relation to treaty regulating joint pursuit of research and development in relation to nuclear power)
ICSID Arbitration against Cyprus (claim for compensation for expropriation of a financial services provider)
R(Newby) v. FSA, European Commission (application for contempt against European Commission for interference in the application of an English court’s order for injunction)
Mothers of Srebrenica v Office of the Prosecutor ICTY/UN Security Council (representing next of kin of victims over treatment by the Office of the Prosecutor of the ICTY in relation to the treatment of artefacts recovered from mass graves in Bosnia)
Mangouras v. Spain (The Prestige) ECHR Grand Chamber (Law of the Sea – pollution – whether arrest and detention of master lawful under Article 5(3) ECHR)
Georgias v. Council CJEU (challenge to international sanctions imposed by EU on independent minister of Zimbabwe and claim for damages)
Região autónoma dos Açores v Council CJEU (Law of the Sea – challenge by the Regional Government of the Azores to the legality of EU bottom trawling regulation)

European Law

Very experienced advocate in the CJEU & former chair (2010-2015) of the CCBE bar-bench liaison committee with the Court (PD Lux). Specialising in regulatory, competition and state aid applied across a very wide range of industries, including telecoms, electronics, IT (Big Tech), chemicals, materials for the construction industry, food & beer/alcoholic drinks. See also Regulatory and Public law above.

Eleanor Sharpston v. la Cour de Justice de l’Union Européenne CJEU (termination of Advocate General’s term of office; whether reviewable act in EU law)
Bayer v. European Commission, CJEU (whether European Commission prohibition of that pesticide infringed procedural protection under the terms of the authorisation)
R (Newby Foods) v. Food Standards Agency Supreme Court (interpretation of the EU food law in relation to innovative food production processes not foreseen at the time of drafting the regulatory scheme)
Govia Gtr Railway Ltd v The Associated Society of Locomotive Engineers and Firemen Court of Appeal (whether a trade disputed allegedly designed to remove a French company as owner arguably could qualify as a restriction on the EU freedom of establishment)
BA v. Sindicato Español de Pilotos de Lineas Aereas Commercial Court (SEPLA, as Spanish pilots’ trade union, refused to accept sale of Iberia to IAG and totally opposed the creation of a cut price subsidiary, Iberia Express – whether cause of action based on freedom of establishment and to provide cross border services was justiciable in the English courts)
Repertoire Culinaire v. HMRC CJEU (correct classification for the purposes of excise duty of cooking wine to which salt & pepper had been added)
R (Fisher) v. Ministry of Agriculture CJEU (rights of defence in administrative proceedings – obligation to disclose information – interpretation of penalties regime)

Arbitration

Experienced litigator and regularly acts as counsel in arbitral tribunals, often where EU, competition or foreign law issues arise – in appropriate circumstances also acts as expert witness. Can litigate/arbitrate in French and with underlying documents in German, Spanish and Italian. Also sits as an arbitrator.

United Kingdom v. European Union, (Dispute resolution process under Trade and Cooperation Agreement, in relation to failure of EU to perform collaboration in scientific research provisions in Part V re Horizon, Copernicus, Euratom – lead counsel for the United Kingdom under the dispute resolution provisions of the TCA)
Arbitration in relation to US sanctions on Iranian companies (Iranian state entity contracted with German business – US sanctions introduced against Iranian entity – German business also having US interests – German business claiming to avoid contract – Iranian entity pleading EU Blocking Regulation)
Arbitration arising out of share sale agreement between Greek and Italian shipping lines (Greek debt crisis – choice of mix of Greek and Italian law – scope and nature of the obligation of good faith)
Arbitration on effect of EC competition law on specialist shipping pool (common agreements voluntarily entered into between all members of a specialist shipping pool – whether agreements contrary to Article 101 TFEU and/or Chapter 1 and unlawful)
Arbitration Greek company v German Company (subject to Greek and English laws plus Swiss curial law, ICC, Geneva re substantial energy infrastructure – whether German engineering company contractually liable to Greek owners for design errors in design)
Arbitration re expropriation of financial services provider, ICSID (whether alleged abuse of right by state in the application of EU Banking Recovery and Resolution directive breached the fair and equitable treatment clause of the relevant bilateral investment treaty)