Call 1993 | Silk 2009
“Leigh-Ann is a truly special barrister. Her incredible intellect is matched by her flawless judgment. She is a peerless advocate, inspiring confidence in the court and client alike. She is an excellent leader of a team, deploying diverse talents to the greatest effect.”
Legal 500
Oliver Duane
Team Leader
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Jamie Thomas
Team Leader Assistant
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Leigh-Ann is a leading advocate, international arbitrator and mediator.
Her practice includes insurance and reinsurance, group litigation, arbitration, product liability, professional negligence and discipline, administrative and public law and commercial and IT-related disputes. She works both domestically and internationally. She is a Registered Foreign Lawyer at the Singapore International Commercial Court and is also called to the Bar of the Republic of Ireland.
She is President of the Panel of Senior Decision-Makers at the Guernsey Financial Services Commission since 2021, having acted as a Senior Decision-Maker from 2014 – 2021. She held the appointment of Deputy High Court Judge from 2016–2022 (including in the Commercial Court 2020-2022). She has acted for the UK Government for over 30 years and held the appointment of First Counsel to the Welsh Government from 2013 to 2016.
She is recognised as a Leading Silk by the legal directories in eight fields. She is currently shortlisted at the Legal 500 Bar Awards 2026 for Silk of the Year and also Group Litigation Silk of the Year. She was named Insurance Silk of the Year 2024 by Chambers & Partners and Group Litigation and Consumer Silk of the Year 2022 by Legal 500. In 2025, Leigh-Ann was named ‘Women in Law: Bar Champion of the Year’ at Legal 500‘s ESG UK Awards and in 2026 was again shortlisted for that award.
She sits as an arbitrator in commercial disputes, with a particular focus on insurance/reinsurance (including Bermuda Form) and life sciences. She has experience of international arbitrations under the ICC, LCIA, SIAC and CIArb institutional rules and ad hoc arbitrations (both international and domestic). She is a member of the Governing Council of the Nani Palkhivala Arbitration Centre in India.
A CEDR accredited mediator and a Fellow of the Royal Statistical Society, she is also an international advanced advocacy trainer and has taught in the UK, Ireland, South Africa, Australia, Malaysia and Singapore.
Pan NOx Emissions Litigation
Acting for the Opel/Vauxhall in defending litigation brought by large numbers of consumers arising out of the manufacturer of diesel engines and alleging breach of NOx Emissions limits and misrepresentation: Various Claimants v Mercedes Benz Group and others [2026] EWHC 1753 (KB) (by which judgment Cockerill LJ overwhelmingly rejected the core allegations brought on behalf of 1.6 million claimants against major car manufacturers claiming that they installed prohibited defeat devices in their vehicles); Wragg v Opel Automotive GmbH [2024] EWHC 1909 (KB); Wragg v Opel Automobile GmbH [2024] EWHC 1138 (KB); Wragg v Opel Automotive GmbH [2023] EWHC 2632 (KB); Re NOx Emissions Group Litigation [2023] EWHC 3173 (KB); Wragg v Opel Automobile GmbH [2024] EWHC 110 (KB); Various Claimants v Nissan Motor Co Ltd [2024] EWHC 208 (KB); Various Claimants v Mercedes-Benz Group AG [2024] EWHC 695 (KB).
Staley v Financial Conduct Authority
Acting for the Financial Conduct Authority (“FCA”) on an appeal by James (“Jes”) Staley, former CEO of Barclays Bank plc, against the FCA’s decision to impose a prohibition order banning him from holding senior management roles in the financial services industry for having recklessly approved a letter to the FCA which contained misleading statements as to the nature of his relationship with and most recent contact with Jeffrey Epstein. That decision was upheld by the Upper Tribunal: [2025] UKUT 203 (TCC).
Grenfell Civil Claims
Acting for the Royal Borough of Kensington and Chelsea and the Kensington & Chelsea Tenant Management Organisation Ltd in relation to civil claims arising out of the Grenfell Tower fire on 14 June 2017 and related ADR processes, mediated by Lord Neuberger and Bill Marsh, which resulted in settlements of the claim of different groups of claimants between 2023 and 2025: Abdel-Kader & ors v Royal Borough of Kensington and Chelsea & ors [2022] EHWC 2006 (QB); Atmani and others v Royal Borough of Kensington & Chelsea & ors [2022] EWHC 2618 (KB); Abdel-Kader & ors v Royal Borough of Kensington & Chelsea & ors [2021] EWHC 2016 (QB); De Costa & ors v The London Fire Commissioner and ors [2020] EWHC 2718 (QB).
Various Eateries Trading Ltd v Allianz Insurance Plc
Acting for Various Eateries on a claim for business interruption insurance losses arising out of COVID-19 seeking to resolve uncertainty as to issues arising over post-policy period causation and aggregation and a subsequent appeal to the Court of Appeal: [2024] EWCA Civ 10; [2022] EWHC 2549 (Comm).
Financial Conduct Authority v Arch & ors
Acting for the Financial Conduct Authority on its test case under the Financial Markets Test Case Scheme on business interruption insurance and whether certain policies responded to claims arising from the coronavirus pandemic: Financial Conduct Authority v Arch & ors [2020] EWHC 2448 (Comm).
Leigh-Ann has experience in judicial review claims and additionally on civil claims which raise public law or human rights issues. She also has experience of wider administrative/public law issues in the context of tribunal and regulatory law, inquest procedures, legal complaints procedures, financial services regulation, healthcare policy and immigration law. Leigh-Ann has sat in the Administrative Court as a Deputy High Court Judge and is general editor of Human Rights and Civil Practice (OUP). She is ranked by Legal 500 for Administrative & Public Law stating: “Leigh-Ann is a flawless advocate. She is engaging and persuasive, and delivers arguments with absolute clarity. Her advice is not only legally excellent but also pragmatic, giving a clear way through even the most complicated issues.” (Legal 500, 2026).
Advising a financial institution on a potential judicial review challenge to proposed regulatory action.
Advising a manufacturer who was the subject of proposed regulatory action in relation to its products on a potential judicial review challenge.
Advising a UK government department in a sensitive policy context against the backdrop of a potential judicial review challenge.
Advising in relation to a judicial review challenge against the Financial Ombudsman Service arising out of its handling of an insurance complaint.
Advising in relation to a potential judicial review relating to the application of money-laundering regulations.
Advising in relation to the licensing regime for cryptocurrency operators.
Browarek v Smart Solutions (Recruitment) Ltd & FS Commercial Limited (2022-2025)
Representing a labour supply contractor and umbrella solution and payroll service provider in defending multiple civil claims in the High Court arising in the context of modern slavery and human trafficking.
R (Kamlesh Mansukhlal Damji Pattni) v Secretary of State for the Home Department (2019)
Acting for a claimant in his successful application for Judicial Review of a UK Home Office decision refusing his application to British citizenship and refusing to issue him with a British passport.
Advising a senior individual called to give evidence before a parliamentary select committee and a judge-led public inquiry.
Advising on whether various heads of loss, including loss of profits, were recoverable under Article 1 of the First Protocol to the ECHR in a commercial action.
R (on the application of Boehringer Ingleheim Ltd) v NHS Commissioning Board [2016] EWHC 1557 (Admin).
Acting for the claimant in a challenge to a pharmaceutical commissioning decision.
R (on the application of Forge Care Homes Ltd & Ors) v Cardiff & Vale University Health Board & Other Health Boards & County Council of the City of Cardiff & Other Councils & The Welsh Ministers) [2015] EWHC 601
Acting for Welsh Ministers.
Acting for the Ministry of Defence in relation to issues of combat immunity and procurement in the context of claims by service men and women for noise-induced hearing loss caused during or in preparation for operational deployment: see Durrheim v Ministry of Defence [2014] EWHC 1960, QB, an appeal to the High Court arising out of an application for conjoined case management of such claims.
R (on the application of McVey & Ors) v Secretary of State for Health (2010) Med LR 204 (main claim); R (on the application of McVey & ors) v Secretary of State for Health & (1) Jonathan Simms (2) Holly Mills (Interested Parties) [2010] EWHC 1225 (Admin) (interested parties' claim)
Defending a judicial review claim on behalf of the Secretary of State for Health by various claimants and a further claim made by two interested parties which sought to challenge the vCJD Compensation Scheme.
Acting as Counsel to a public inquiry into NHS Complaints Procedures and the Conduct of an NHS gynaecologist, Richard Neale.
Acting for a pharmaceutical company in a potential judicial review challenge to a commissioning decision in relation to its product. Case settled at pre-action stage.
Acting on behalf of the Ministry of Defence in relation to 12 conjoined appeals to the Upper Tribunal against the First-tier Tribunal (Armed Forces Compensation and War Pensions Chamber)’s decision not to award pensions to certain veterans of the nuclear tests in Australia and the South Pacific in the 1950s. The appeal raised jurisdictional issues regarding the legal test to be applied by the First-tier Tribunal and the Upper Tribunal’s powers of review.
Advising in relation to a legal challenge to the grant of marketing authorisation in respect of a pharmaceutical product under EU and domestic law.
R (Lord Chancellor) v Chief Land Registrar [2006] QB 795
Acting for a local authority challenging the expropriatory effect of legislation.
R (Ministry of Defence) v Wiltshire and Swindon Coroner [2006] 1 WLR 134
Acting for the Ministry of Defence as claimant challenging a jury direction in an inquest.
Leigh-Ann has experience of acting or advising in a wide range of commercial and contract disputes including sale of goods, agency, share purchase agreements, licensing, IT contractual issues etc. She also regularly advises and acts in relation to financial services issues. Leigh-Ann is a Registered Foreign Lawyer at the Singapore International Commercial Court.
Acting for a pharmaceutical company in a high value licensing dispute with another pharmaceutical company.
Advising a specialist supplier regarding enforcement of contractual limitations of liability in defence of a high value fire claim.
Acting for a Singapore technology company in defence of a high value licensing dispute with a global technology company.
Emblaze Mobility Solutions Ltd v Revenue and Customers Commissioners [2018] UKUT 373 (TCC)
Acting in an appeal relating to issues of interest and lawfulness of deduction of repayment supplement in a tax case
Akcine Bendrove Bankas Snoras v Antonov [2018] EWHC 887 (Comm)
Acting in an application regarding whether obtaining of foreign enforcement orders constituted breach of undertakings given on freezing injunction
Goodlife Foods Ltd v Hall Fire Protection Ltd [2018] BLR 491 (CA);[2017] EWHC 767 (TCC); [2017] BLR 389
Acting for the defendant in a commercial dispute arising out of a fire with a claim for negligence and breach of statutory duty in relation to the supply and installation of a fire suppressant system and giving rise to issues over incorporation and validity of exclusion clauses
Acting for a bank on a Privy Council appeal in litigation arising from a dispute over the status of a mortgage over land and enforcement of its security.
Acting in a referral and appeal to the Court of Appeal on behalf of a financial services company in a financial services enforcement case.
Advising a software developer and IT solutions contractor regarding various contractual disputes arising out of a Software Development & Managed Services Agreement.
Advising claimants in relation to their appeal and mitigation options following a failed claim against an international bank arising out of lost investments.
Acting on behalf of Welsh Ministers in a substantial competition law claim against Servier in the Chancery Division, concerning the supply of the ACE inhibitor, Perindopril.
Acting on behalf of Welsh Ministers in a substantial competition law follow-on claim being tried in the Chancery Division against Reckitt-Benckiser to recover losses to the Welsh NHS as a result of anti-competitive conduct relating to its product, Gaviscon.
Abbey Forwarding (in Liquidation) v Revenue and Customs Commissioners [2015] EWHC 225 (Ch); [2015] Bus LR 882
Representing an insolvent company and succeeding in enforcing a cross-undertaking in damages given by HMRC when seeking an order appointing a provisional liquidator of the company
Secretary of State for the Home Department v Raytheon Systems Ltd [2015] 1 Lloyd’s Rep 493 and [2014] EWHC 4375
Acting in a very substantial international commercial arbitration involving a high value and complex IT dispute arising out of the “e-Borders” system. TCC (two judgments) Leigh-Ann acted for the Home Secretary and succeeded in overturning a high value arbitration award for serious irregularity
Acting in Commercial Court proceedings by financial companies who are alleging negligence on the part of their insurance broker in failing to ensure they had coverage for claims arising out of PPI mis-selling.
Acting for a firm in a challenge to enforcement action by the Financial Conduct Authority. Obtained order staying enforcement action.
Advising in relation to a proposed retail banking claim arising out of alleged negligence in relation to cheque fraud.
Acting on a claim for insurance and investment fraud made by a financial services regulator against the former directors of CLICO, a Trinidadian company with business across the Caribbean.
Acting on behalf of various insurers in the credit hire context on issues of re-trial and future case management arising out of the test cases decided by the Court of Appeal.
Acting on a £4 million+ claim by a company against its former CEO and director for breaches of fiduciary and contractual duties.
Acting for the claimant in relation to two serious commercial fraud cases arising out of property transactions.
Leigh-Ann is ranked by both Legal 500 and Chambers & Partners for Financial Services with quotations for this field including that “Leigh-Ann is a truly special barrister. Her incredible intellect is matched by her flawless judgement. She is a peerless advocate, inspiring confidence in the court and client alike. She is an excellent leader of a team, deploying diverse talents to the greatest effect.” (Legal 500, 2026), “Leigh-Ann is phenomenally good and is a first-class operator” (Chambers & Partners 2026) and “…is one of those people that really help you relax in court and will never put a foot wrong” (Chambers & Partners 2026). Leigh-Ann has been a Senior Decision-Maker for the Guernsey Financial Services Commissions since 2014 and President of the Panel of Senior Decision-Makers since 2021.
Advising in relation to regulatory issues arising out of motor finance compensation / redress.
Staley v Financial Conduct Authority [2025] UKUT 203 (TCC).
Acting for the Financial Conduct Authority on an appeal by James (“Jes”) Staley, former CEO of Barclays Bank plc, against its decision to impose a prohibition order banning him from holding senior management roles in the financial services industry. Mr Staley had approved a letter which the Bank sent to the FCA in the knowledge that it contained misleading statements as to the nature of his relationship with and most recent contact with Jeffrey Epstein. That decision was upheld by the Upper Tribunal. See also decisions made in relation to procedural applications in that case [2024] UKUT 394 (TCC).
Financial Conduct Authority v Arch & ors [2020] EWHC 2448 (Comm).
Acting for the Financial Conduct Authority on its test case (which was the first case under the Financial Markets Test Case Scheme) on business interruption insurance and whether it responded to claims arising from the coronavirus pandemic.
Advising on issues relating to pricing practices.
Advising on issues relating to cryptocurrency and money laundering regulation.
Advising in relation to the handling of complaints by the Financial Ombudsman Service.
Challenging a financial services regulatory decision made by the Financial Conduct Authority on behalf of an insurance company.
Leigh-Ann has specialised in group litigation for most of her career at the Bar, acting in numerous high value and complex matters in her career, across a range of sectors including automotive, defence, insurance, medical devices and pharmaceuticals. Leigh-Ann is ranked by both Chambers & Partners and The Legal 500 for her Group Litigation work. She is shortlisted for Group Litigation & Consumer Silk of the Year by The Legal 500 in 2026. She was named ‘Group Litigation & Consumer Silk of the Year in 2022 by The Legal 500. Quotations for this field include: “She is in a class of one. She has the key skills for group litigation. She understands the need to think twelve moves ahead, years ahead; she can play that 3D game of chess. That’s her sweet spot.” (Chambers & Partners, 2026) “She is a fantastic barrister with a huge amount of experience on group litigation. She is definitely up there among the best at this work.” (Chambers & Partners, 2026) “She is a terrifically hard worker. Clients love her. A great advocate.” (Legal 500, 2026)
Pan NOx Emissions Litigation
Acting for the Opel/Vauxhall in defending litigation brought by large numbers of consumers arising out of the manufacturer of diesel engines and alleging breach of NOx Emissions limits and misrepresentation: Various Claimants v Mercedes Benz Group and others [2026] EWHC 1753 (KB) (by which judgment Cockerill LJ overwhelmingly rejected the core allegations brought on behalf of 1.6 million claimants against major car manufacturers claiming that they installed prohibited defeat devices in their vehicles); Wragg v Opel Automotive GmbH [2024] EWHC 1909 (KB); Wragg v Opel Automobile GmbH [2024] EWHC 1138 (KB); Wragg v Opel Automotive GmbH [2023] EWHC 2632 (KB); Re NOx Emissions Group Litigation [2023] EWHC 3173 (KB); Wragg v Opel Automobile GmbH [2024] EWHC 110 (KB); Various Claimants v Nissan Motor Co Ltd [2024] EWHC 208 (KB); Various Claimants v Mercedes-Benz Group AG [2024] EWHC 695 (KB).
Covid-19 in Care Homes Claims
Acting for a group of care homes in defence of a group action arising out of alleged negligence in the contraction of COVID-19 during the pandemic.
Grenfell Tower Fire Civil Claims
Acting for Royal Borough of Kensington and Chelsea and the Kensington & Chelsea Tenant Management Organisation Ltd in relation to over 1,200 civil claims arising out of the Grenfell Tower fire on 14 June 2017 and related ADR processes, mediated by Lord Neuberger and Bill Marsh, which resulted in settlements of the claim of different groups of claimants between 2023 and 2025: Abdel-Kader & ors v Royal Borough of Kensington and Chelsea & ors [2022] EHWC 2006 (QB); Atmani and others v Royal Borough of Kensington & Chelsea & ors [2022] EWHC 2618 (KB); Abdel-Kader & ors v Royal Borough of Kensington & Chelsea & ors [2021] EWHC 2016 (QB); De Costa & ors v The London Fire Commissioner and ors [2020] EWHC 2718 (QB).
Hormone Pregnancy Tests Litigation
Acted for the Department of Health and Social Care in relation to over 200 civil claims brought against pharmaceutical companies and the medicines’ regulator for damages for personal injuries allegedly caused by hormone pregnancy tests ingested in the 1960s and 1970s: Wilson v Bayer Pharma AG [2023] EWHC 1282 (KB).
FCA High Court test case on business interruption during the coronavirus pandemic
Acted for the FCA in obtaining court declarations against eight insurers aimed at resolving contractual uncertainty in selected business interruption insurance policies, following the large numbers of claims made to insurers under these policies arising out of the coronavirus (COVID-19) pandemic and resulting Government controls imposed: FCA v Arch & others [2020] EWHC 2448 (Comm).
Atomic Veterans Litigation
Appearing at the limitation trial and subsequent appeals to the Court of Appeal and Supreme Court for the Ministry of Defence in a major group action by over 1000 former servicemen arising out of the nuclear tests in Australia and the South Pacific in the 1950s: AB & ors v Ministry of Defence [2009] EWHC 1421; (2011) 117 BMLR 101, CA; [2012] 2 WLR 643, SC.
The Foetal Anticonvulsant Litigation.
AIDS/HIV and Hepatitis C Haemophiliacs litigation.
The Human Growth Hormone/CJD Litigation
Acting for the Department of Health and Medical Research council in defending claims both by those who had contracted Creutzfeldt-Jakob Disease and the “worried well” ((2000) 54 BMLR 1, 79, 85, 95, 100, 103, 104, 111; [2000] Lloyd’s Rep Med 161).
The Porton Down Litigation
Representing the Ministry of Defence between 2003 and 2008, dealing with a six-and-a-half-month inquest in 2004, a subsequent judicial review and claims arising out of non-therapeutic human experimentation with chemical warfare agents. The litigation involved extensive expert evidence on toxicology and the development of bioethics from 1940s to 1980s.
BSE/vCJD Litigation
Acting on behalf of the Department of Health and DEFRA in relation to claims arising out of BSE/variant CJD and involved in setting up the vCJD Trust to compensate victims of vCJD.
Acting in relation to a proposed vaccine damage group action.
Ranked by Chambers & Partners and Legal 500 as a Leading Silk for Insurance & Reinsurance, Leigh-Ann was named ‘Insurance Silk of the Year’ by Chambers & Partners in 2024. Quotations for this field include: “She is sensational and very adept at managing strategy and the client towards sensible outcomes. There is no one better at steering large litigation.” (Chambers & Partners, 2026), “Leigh-Ann Mulcahy is totally excellent. She is a calm and compelling advocate.” (Chambers & Partners, 2026) and “Leigh-Ann has got such a successful broad practice asking for policyholders and insurers. She is great on her feet and is a very effective cross-examiner.” (Chambers & Partners, 2026), “Leigh-Ann is careful and considered and always completely masters the material. Leigh-Ann has been perfect. So refreshing that she combines intellectual excellence with user friendliness.” (Legal 500, 2026).
Leigh-Ann has expertise in many areas of insurance and reinsurance including professional indemnity, employers’ liability, public liability, civil liability, financial lines, business interruption, event cancellation, property, marine, credit insurance, fidelity and cyber risks (in both litigation and arbitration). She has considerable expertise in relation to insurance claims for COVID-19 losses, the insurance of asbestos liabilities and issues that arise in the insurance of financial services professionals (particularly in relation to consumer redress and the misselling of PPI, pensions and other investments).
Various Eateries Trading Limited v Allianz Insurance Plc
Acting for Various Eateries on a claim for business interruption insurance losses arising out of COVID-19 seeking to resolve uncertainty as to issues arising over post-policy period causation and aggregation and a subsequent appeal: [2024] EWCA Civ 10; [2022] EWHC 2549 (Comm).
Cuckow v AXA Insurance UK Plc
Acting for AXA in relation to a test case involving up to 1800 other claims in which third party claimants seek an indemnity from an insurer under the public liability section of a policy issued to its insolvent insured company arising out of its alleged negligent installation of cavity wall insulation. The litigation is testing issues relating to beaches of condition relating to claims notification and claims procedures by the administrators of the insured. Leigh-Ann succeeded on behalf of insurers at trial and on appeal. Cuckow v AXA Insurance UK Plc [2023] EWHC 701 (KB)
Financial Conduct Authority v Arch and others [2020] EWHC 2448 (Comm)
Acting for the FCA on its test case relating to business interruption insurance and whether it responds to COVID-19 losses.
Various Claimants v Giambrone & Law (A firm) [2019] 4 WLR 7
Acting for AIG on an appeal to the Court of Appeal against a non-party costs order made against liability insurers pursuant to section 51 Senior Courts Act 1981 arising out of group litigation. Settled with the appeal being allowed and the order set aside.
Redman v Zurich Insurance Plc [2017] EWHC 1919
Acting for insurers on one of the first claims under the Third Parties (Rights against Insurers) Act 2010 concerning its retrospective effect.
International Energy Group Ltd v Zurich Insurance [2016] AC 509, SC
Successfully acting for Zurich before Court of Appeal and Supreme Court on insurance issues arising out of asbestos liabilities.
Cape Distribution Limited v Cape Intermediate Holdings Limited [2016] EWHC 1119 & [2016] EWHC 1786
Acting for Cape Intermediate Holdings Ltd in proceedings before Picken J brought by Aviva to recover its outlay on behalf of a Cape subsidiary for asbestos-related disease. This concerned issues of parent liability, contractual indemnities, co-insurance and subrogation. This resulted in two major judgments and a six-week avoidance trial heard in January/February 2017, following which the case, which was on appeal to the Court of Appeal, settled.
Ocean Finance & Mortgages Ltd v Oval Insurance Broking Ltd [2016] Lloyd’s Rep IR 319
Acting for a multinational financial services company in relation to professional indemnity insurance issues arising out of PPI mis-selling liabilities and a claim against its brokers. The claim settled shortly before a trial which proceeded solely in relation to the third-party action.
Durham v BAI & Ors [2012] 1 WLR 867, SC
Successfully acting for Zurich in the Employer’s Liability Policy Trigger Litigation relating to coverage of asbestos liabilities up to and including the Supreme Court.
Extensive advisory work on insurance and reinsurance issues e.g.:
Leigh-Ann is ranked by Chambers and Partners for International arbitration: Arbitrators. Quotations in this field include “Leigh-Ann Mulcahy is very thoughtful, considered and she gets to grips with the papers. She is very respectful and focused.” (Chambers & Partners, 2026) and “Leigh-Ann Mulcahy is very responsive and she knew the case inside out.” (Chambers * Partners, 2026).
Acting as co-arbitrator in two Bermuda Form arbitrations in a high value insurance coverage dispute.
Acting as co-arbitrator in an ad hoc arbitration arising out of coverage for remediation of alleged building defects.
Acting as presiding arbitrator in an LCIA arbitration relating to a commercial licensing dispute arising in the life sciences context.
Acting as co-arbitrator in three ad hoc insurance arbitrations in the UK and Bermuda arising out of coverage disputes on general liability insurance policies.
Acting as co-arbitrator in a SIAC arbitration in an insurance-related dispute.
Acting as co-arbitrator in an LCIA arbitration arising out of a commercial dispute concerning a share purchase agreement and warranties given by the sellers in relation to the businesses being sold.
Acting as sole arbitrator in five related LCIA arbitrations arising in the banking and finance context.
Acting as sole arbitrator in a CIArb arbitration relating to a claim under a guarantee and counterclaim (jointly appointed by the parties).
Acting as sole arbitrator in an LCIA arbitration relating to the oil and gas industry.
Acting as co-arbitrator in an LCIA arbitration relating to an alleged fraud claim.
Acting as sole arbitrator in an ad hoc domestic insurance-related arbitration in a professional liability dispute (jointly appointed by the parties).
Appointed as an ad hoc arbitrator in a commercial dispute relating to quantum.
Acting as leading counsel in an LCIA arbitration relating to a dispute over insurance coverage for strikes, riots and civil commotion in a foreign jurisdiction.
Acting as leading counsel in an ICC arbitration relating to a licensing dispute in the pharmaceutical field.
Acting on behalf of the Home Secretary in a substantial LCIA arbitration which comprised a very high value and complex IT dispute between the UK Government and the British subsidiary of a US defence contractor arising out of the “e-Borders” contract. Leigh-Ann subsequently secured the setting aside of the £200+ million arbitration award for serious irregularity (Secretary of State for the Home Department v Raytheon Systems Ltd [2015] 1 Lloyd’s Rep 493 and also [2014] EWHC 4375, TCC).
Acting for a corporate Singaporean policyholder regarding its claim for indemnity under a credit insurance policy underwritten by UK insurers in a proposed international arbitration, which ultimately settled.
Leigh-Ann is listed as a Leading Silk for Product Liability by the legal directories (Band/Tier 1), is currently shortlisted for Group Litigation and Consumer Silk of the Year (2026) by the Legal 500 and was named Group Litigation and Consumer Silk of the Year 2022 by the Legal 500. Quotations for this field include: “Leigh-Ann Mulcahy is really outstanding. She is extremely dedicated and available and was excellent and well prepared in court.” (Chambers & Partners, 2026) and “Leigh-Ann has meticulous attention to detail and a really amazing work ethic” (Chambers & Partners, 2026). She advises on product liability and product safety in a range of areas including commercial products, pharmaceuticals, medical devices, vaccines, chemicals, radiation and food. She also advises on regulatory issues and legal risk management in order to seek to avoid litigation. She was a Fellow of the Royal Statistical Society frfom 2017 to 2022 and is sought after for cases involving technical and scientific evidence. She is an editor of The Law and Regulation of Medicines (Oxford University Press) and contributor to The Law and Regulation of Medicines and Medical Devices (OUP).
Pan NOx Emissions Litigation
Acting for the Opel/Vauxhall in defending litigation brought by large numbers of consumers arising out of the manufacturer of diesel engines and alleging breach of NOx Emissions limits and misrepresentation: Various Claimants v Mercedes Benz Group and others [2026] EWHC 1753 (KB) (by which judgment Cockerill LJ overwhelmingly rejected the core allegations brought on behalf of 1.6 million claimants against major car manufacturers claiming that they installed prohibited defeat devices in their vehicles); Wragg v Opel Automotive GmbH [2024] EWHC 1909 (KB); Wragg v Opel Automobile GmbH [2024] EWHC 1138 (KB); Wragg v Opel Automotive GmbH [2023] EWHC 2632 (KB); Re NOx Emissions Group Litigation [2023] EWHC 3173 (KB); Wragg v Opel Automobile GmbH [2024] EWHC 110 (KB); Various Claimants v Nissan Motor Co Ltd [2024] EWHC 208 (KB); Various Claimants v Mercedes-Benz Group AG [2024] EWHC 695 (KB).
Sutton and Easter Surrey Water Plc v Monarch Chemicals Ltd [2026] EWHC 1260 (TCC).
Acting for a distributor of products in defence of a product liability claim in the Technology & Construction Court arising out of a chemical delivery incident and in relation to contribution proceedings.
Grenfell Civil Claims
Acting for Royal Borough of Kensington and Chelsea and the Kensington & Chelsea Tenant Management Organisation Ltd in relation to civil claims arising out of the Grenfell Tower fire on 14 June 2017 and related ADR processes, mediated by Lord Neuberger and Bill Marsh, which resulted in settlements of the claim of different groups of claimants between 2023 and 2025. Court judgments include: Abdel-Kader & ors v Royal Borough of Kensington and Chelsea & ors [2022] EHWC 2006 (QB); Atmani and others v Royal Borough of Kensington & Chelsea & ors [2022] EWHC 2618 (KB); Abdel-Kader & ors v Royal Borough of Kensington & Chelsea & ors [2021] EWHC 2016 (QB); De Costa & ors v The London Fire Commissioner and ors [2020] EWHC 2718 (QB).
Acting for a firm of security professionals defending an intimated claim by a former client whose home was burgled.
Acting for a sub-contractor on a multi-party high value claim brought by BAE Systems arising out of the activation of a fire suppressant system in an aircraft testing facility.
Advising on a high value claim arising out of a vehicle fire with international dimensions.
Advising a toy manufacturer on issues relating to a potential product recall and other regulatory issues.
Advising a major manufacturer of household products on commercial product liability claims and compatibility with EU law.
Advising a specialist gas system supplier regarding liability issues arising out of a high value fire claim.
Advising a leading manufacturer on issues arising out of consumer products causing property damage.
Acting on a dispute between two life sciences companies arising out of the termination of a clinical trial.
Goodlife Foods Ltd v Hall Fire Protection Ltd [2017] EWHC 767 (TCC); [2017] BLR 389
Acting for the defendant in a negligence claim arising out of the supply of a fire suppressant system. The claim was subject to a preliminary issue on the validity of an exclusion clause, an issue on which the defendant was successful.
Grundon Waste Management Ltd v Hygrade Industrial Plastics Ltd (2012)
Acting for the claimant in this multi-party action in the TCC arising out of an overheating incident and associated fires at a waste management facility
Costain Oil & Gas Process Limited v Barton Firtop Engineering (2008-2010)
Advising on and settling pleadings in a commercial product liability claim arising out of manufacture and supply of temporary industrial strainers for use in gas pipelines.
Kent County Council v Griggs & Ors; Aviza v Welsh Electrical & Ors
Defending an electrical wholesaler, Newey & Eyre, in relation to commercial product liability / fire claims arising out of allegedly defective capacitors in light fittings.
Advising on claims arising out of the testing and manufacture of a defective building insulation product.
Advising a major manufacturer and its insurers on potential claims arising out of dishwashers and fire risks.
AB & ors v Ministry of Defence [2009] EWHC 1421; (2011) 117 BMLR 101, CA; [2012] 2 WLR 643, SC.
Appearing at the limitation trial and subsequent appeals to the Court of Appeal and Supreme Court for the Ministry of Defence in a major group action by over 1000 former servicemen arising out of the nuclear tests in Australia and the South Pacific in the 1950s.
Appearing on behalf of Ministry of Defence on 12 conjoined war pensions appeals by veterans to the Upper Tribunal.
Advising a pharmaceutical manufacturer in relation to intimated product liability claims in the context of litigation in other jurisdictions.
Advising on legal and regulatory issues relating to stem cell therapy treatment in the UK and/or advertising the provision of such treatment outside the UK.
Sarah Jane Wilson & ors v Bayer Pharma AG, Schering Health Care Ltd, Aventis Pharma Ltd and Secretary of State for Health and Social Care [2023] EWHC 1282 (KB)
Acting for the Department of Health and Social Care (sued in its capacity as medicines regulator) in relation to group litigation arising from the use of hormone pregnancy tests in the 1960s and 70s.
Advising on a potential claim arising out of an anti-smoking treatment.
Advising on potential product liability claim arising out of a monoclonal antibody used in cancer screening.
Advising on a claim relating to dopamine agonists/compulsive gambling.
Advising in relation to The Foetal Anticonvulsant Litigation arising out of an anti-epileptic pharmaceutical treatment.
Advising in relation to the AIDS/HIV and Hepatitis C Haemophiliacs’ litigation.
Defending a parallel importer in relation to a pharmaceutical claim relating to an allegedly defective patient information leaflet.
Amanda Smith v Secretary of State for Health [2002] Lloyd’s Med 305
Defending the Committee on the Safety of Medicines in the Aspirin/Reye’s Syndrome case.
Acting in The Human Growth Hormone/CJD Litigation in relation to both those who had contracted CJD and claims by the “worried well” ((2000) 54 BMLR 1, 79, 85, 95, 100, 103, 104, 111; [2000] Lloyd’s Rep Med 161).
Carrying out specialist advisory work in relation to pharmaceutical regulation and legal risk management for producers, insurers and regulatory bodies.
Working with the Royal Statistical Society to consider how to improve the use and understanding of epidemiological and statistical evidence in civil litigation.
Acting on behalf of a clinic defendant in the PIP Breast Implant Litigation arising out of the use of industrial (as opposed to medical) grade silicone in breast implants by a French company.
Advising a major multinational company in relation to its regulatory obligations and a possible product recall of a medical device.
Advising a manufacturer of cosmetic dermal fillers in relation to claims against it arising out of granuloma formation.
Advising on liability for allergies alleged to be the result of PPD in hair dye.
Representing the Ministry of Defence in the Porton Down litigation between 2003 and 2008, dealing with a six-and-a-half-month inquest in 2004, a subsequent judicial review and claims arising out of non-therapeutic human experimentation with chemical warfare agents. The litigation involved extensive expert evidence on toxicology and the development of bioethics from 1940s to 1980s.
Acting on behalf of the Department of Health and DEFRA in relation to claims arising out of BSE/vCJD and involved in setting up the vCJD Trust to compensate victims of vCJD.
Acting in relation to a proposed vaccine damage group action.
Leigh-Ann advises and acts on professional disciplinary cases in relation to the Solicitors Regulation Authority and Bar Standards Board.
Advising a senior solicitor in relation to an SRA investigation and potential SDT proceedings.
Defending a barrister in disciplinary proceedings before a BTAS Disciplinary Tribunal.
Acting for a law firm in defending wasted costs proceedings involving allegations of misconduct in parallel with professional disciplinary proceedings.
Acting for a barrister in relation to judge initiated wasted costs proceedings arising out of a high-profile criminal trial.
Advising a law firm in relation to regulatory issues relating to licensing as an ABS and anti-money laundering regulations.
Advising a law firm in relation to conflict of interest and confidential information issues in the context of leveraged finance transactions.
Advising a law firm in relation to issues over the Solicitors’ Account Rules and protection of client monies.
Defending an accountant and non-executive director in regulatory proceedings brought by the Financial Reporting Council arising out of the collapse of a financial institution.
Advising in relation to a disciplinary case before the Royal College of Veterinary Surgeons Disciplinary Committee.
Leigh-Ann is listed as a Leading Silk for Professional Negligence by Chambers & Partners and the Legal 500. Quotations for this field include “Leigh-Ann Mulcahy KC is involved in huge cases and is a strong advocate.” (Chambers & Partners, 2026) and “Leigh-Ann Mulcahy KC is used to dealing with very high-value professional negligence.” (Chambers & Partners, 2026) and “Leigh-Ann is brilliant and very receptive.” (Chambers & Partners, 2026). She has extensive expertise in professional liability including wasted costs applications, issues of professional conduct including conflicts of interest, claims for lost litigation and loss arising from disadvantageous transactions, and claims arising in the criminal or regulatory context, product liability context or which raise human rights issues.
Defending an accountants/tax advisers’ negligence claim on behalf of MRI Moores Rowland LLP.
Bezant v Rausing & 16 ors [2007] EWHC 1118
Representing the UK and Cayman branches of a firm of accountants and tax advisers in a substantial case involving alleged breaches of the company and insolvency legislation and professional negligence.
Acting for an architect on a £20 million claim arising out of alleged negligence in designing a modification to a factory which was subsequently destroyed by fire.
Advising on claim against engineer arising out of a defective floor slab in a major commercial development.
Acting for firm of engineers in relation to claims arising out of a defective industrial crane.
Dealing with claims against surveyors and valuers in relation to both residential and commercial valuation claims. Expertise in marine surveyors’ liabilities.
Ocean Finance & Mortgages Ltd v Oval Insurance Broking Ltd [2016] Lloyd’s Rep IR 319
Acting for a multinational financial services company in relation to claims against producing and placing brokers arising out of failure to make a notification and/or alleged non-disclosure to insurer of material information leading to avoidance of cover. The claim settled shortly before trial which proceeded in relation to the third party action.
Acting for insurance brokers in relation to a claim of alleged negligence arising out of the scope of their customer’s cover.
Shand v Kemkers & ors [2026] EWHC 341 (KB).
Acting for partners or former partners in two law firms (Mishcon de Reya LLP and DWF LLP) in defending contempt proceedings brought by a litigant in person arising out of long-running litigation concerning defects in a flat. The contempt proceedings were struck out as an abuse of process and as largely an attempt to relitigate settled or discontinued claims.
Acting for a silk in relation to a high value claim arising out of failed group litigation. The claim was subsequently discontinued.
Acting for a firm of solicitors in defence of a negligence claim and wasted costs proceedings brought by former clients alleging liability to compensate for loss arising from the handling of a dispute with another party.
Advising a leading law firm on a high value claim by a former client arising out of advice given in litigation regarding the status of an offer to settle.
Coote v Ullstein [2022] EWHC 607 (QB).
Acting for a silk on a successful application for summary judgment on a professional negligence claim by a former client in connection with the failed MMR Litigation.
Acting for a KC and junior in defending a potential high value negligence claim arising out of lost litigation.
Acting for a claimant solicitors’ firm suing former clients for unpaid fees and defending substantial counterclaims for alleged negligence.
Acting for solicitors in defence of a breach of fiduciary duty claim.
Paragon v Plevin (2017)
Defending a wasted costs claim in the Supreme Court against a firm of solicitors.
Hassan Khan & Co v Al Shanfari & Al Rawas [2017] EWCA Civ 42
Acting on a limitation appeal to the Court of Appeal in a solicitor’s liability case where a counterclaim alleging negligence was raised in defence of a claim for unpaid fees.
Defending a very high value solicitors’ negligence claim arising out of lost product liability litigation, which settled at mediation.
Defending a high value wasted costs claim arising out of failed employment tribunal proceedings.
Defending a High Court claim on behalf of a firm of solicitors arising out of a property transaction involving allegations of dishonest assistance in a breach of trust.
Acting for insurers of a licensed conveyancer in relation to a number of claims arising out of alleged lending transactions.
Appearing on a s.33 Limitation Act 1980 application on behalf of claimants whose solicitors who had wrongly obtained extensions of time for service of first claim forms leading to the claims being struck out and had to bring fresh claims on behalf of their clients.
Griswold v Mace Jones & anr (2013)
Defending a silk in proceedings in the Chancery Division by former clients against their solicitors and counsel arising out of lost commercial litigation.
Advising a commercial client on the merits and quantum of a proposed claim against two former firms of solicitors arising out of a failed business venture involving a disqualified director.
Medcalf v Mardell [2003] AC 120
Representing the respondent barristers to the first wasted costs case to be heard by the House of Lords.
Phillips and ors v Symes & ors (No 2) [2005] 1 WLR 2043, [2004] EWHC 2330 (Ch)
Acting for the expert in the first claim for wasted costs against experts.
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