Gethin Thomas

Gethin specialises in environmental law. He is ranked as a ‘rising star’ in environmental law by the Legal 500 (2024).

Gethin is regularly instructed to advise on a broad range of environmental matters. Gethin has extensive experience of environmental judicial review challenges, and climate change litigation. He has acted in a number of high-profile and significant environmental cases, in particular, concerning nationally significant infrastructure projects.

He has also advised NGOs, central and local government, regulators (including the Environment Agency, Natural Resources Wales and Ofgem), developers and other private companies on a broad array of environmental law issues. These include, for example, water resources, air quality, contaminated land, the Aarhus Convention, SEA, EIA, and Habitats assessments, as well as issues arising under other discrete statutory regimes such as, for example, the Animal Health Act 1981, Forestry Act 1967, and the Hedgerows Regulations 1997.

Gethin is a contributing editor of the Environmental Law Bulletin (published by Sweet & Maxwell). He is also a member of LexisNexis’ Q&A Expert Panel on environmental law.

Gethin also has particular experience in energy regulation. He has particular expertise in oil and gas regulation under the Petroleum Act 1998. He also has experience in the regulation of nuclear power, which includes advising the holder of a nuclear site licence.

Notable recent instructions include:

• R (on the application of Barclay) v Secretary of State & Gatwick Airport Limited [2026] EWHC 1556 (Admin): As junior counsel, led by Alex Goodman KC, acting on behalf of the Claimant in a judicial review of the grant of a development consent order for Gatwick Airport expansion, by its northern runway project.
• Re Ackworth Recycling Yard (2026): Acted as sole counsel, on behalf of the Environment Agency, in the successful defence of an appeal against the revocation of an environmental permit.
• R (on the application of Nobel Oil E&P North Sea Ltd) v The Oil and Gas Authority t/a The North Sea Transition Authority [2025] EWHC 2139 (Admin): As junior counsel, led by Victoria Hutton, acting on behalf of the Secretary of State, an interested party in a challenge to decommissioning decisions taken by the North Sea Transition Authority.
• Havant Biogas and ors v Ofgem (2025): Acted on behalf of Ofgem, in an A1P1 damages claim for alleged loss of goodwill in respect of a biomethane production project, led by Jason Coppel KC and Angharad Parry. The claim settled shortly before trial.
• R (on the application of Jennifer Dawes) v Secretary of State and Anor [2024] EWCA Civ 560: Acted on behalf of the Claimant, as junior counsel to Richard Harwood OBE KC, in a judicial review challenging the second grant of development consent for the re-opening of Manston Airport in Kent, on climate change and need grounds. Gethin previously acted on behalf of objectors to the scheme, instructed by the Environmental Law Foundation, in respect to its climate change impacts. Gethin also acted as junior counsel to Paul Stinchcombe KC and Richard Wald KC in a successful judicial review challenging the first grant of the development consent order in 2021. For more information on the first claim, please see here.
• R (on the application of Greenpeace UK) v Secretary of State and the OGA [2023] EWHC 2608 (Admin): Acted on behalf of Greenpeace UK, in a judicial review challenging a series of decisions culminating in the launch of the 33rd UK Offshore Oil and Gas Licensing Round by the North Sea Transition Authority, with James McClelland KC and Alastair Richardson.
• R (on the application of Transport Action Network Ltd) v Secretary of State and National Highways [2023] EWHC 860 (KB): Acted as junior counsel in a judicial review challenge to the grant of a development consent order for the A428 Road Improvement Scheme, on biodiversity and climate change grounds, led by Estelle Dehon KC.
• R (on the application of Tarian Hafren Severn Shield Cyf) v Marine Management Organisation [2022] EWHC 683 (Admin): Acted as junior counsel, led by David Wolfe KC, in a judicial review challenging a marine licence issued by the Marine Management Organisation, granting permission to dispose of mud, dredged during the course of the construction of Hinkley Point C nuclear power station, in the Severn Estuary. For more information, please see here.
• R (on the application of Transport Action Network Ltd) v Secretary of State: Acted as junior counsel, in a judicial review challenging the Secretary of State’s decision not to suspend the National Policy Statement for National Networks pending its review, led by David Wolfe KC and Peter Lockley.
• All Wales (Rod Fishing and Net Fishing) Byelaws: Acted as junior counsel to Richard Wald KC, instructed by Natural Resources Wales, in a four-week Inquiry concerning the implementation of byelaws for the conservation of salmon and sea trout stocks in Welsh rivers. For more information, please see here.
• Advice on Environmental Bill: Advising ClientEarth, as junior counsel to Stephen Tromans KC, in respect of draft clauses of the Environment Bill. The advice was cited during the House of Lords second reading of the Environment Bill.
• EIR: Assisted Nigel Pleming KC in relation to a matter arising from the scope of the definition of ‘public authority’ pursuant to the Environmental Information Regulations 2004.
• Coal Authority and the Coal Industry Act 1994: Assisted Andrew Tabachnik KC in advising on issues arising under the Coal Industry Act 1994.
• Climate change and planning: Assisted Peter Village KC in advising as to climate change’s role in the planning system.
• UNCITRAL arbitration: Acted as junior counsel in an ad hoc arbitration in the energy sector, raising climate change issues, led by Gordon Nardell KC.
• Application of SEA and Habitats Directives to the CAA’s Airspace Change Masterplan: Provided strategic advice to the Civil Aviation Authority, as sole counsel, in respect of the applicability of the SEA and Habitats Directives to the preparation of an Airspace Change Masterplan.

Gethin has a specialist planning and infrastructure practice. He regularly acts in planning challenges before the High Court, for both claimants and defendants, as well as in major planning inquiries.

Gethin is ranked as a ‘rising star’ in planning law by The Legal 500 (2025). He was ranked as one of the ‘Highest Rated Planning Juniors Under 35′ by Planning Magazine (2020).

He has particular experience of Development Consent Orders for Nationally Significant Infrastructure Projects under the Planning Act 2008. He is currently acting in the challenge to the Gatwick Airport DCO. He previously acted in one of the first successful judicial review challenges to the grant of a DCO, concerning Manston Airport. He has also acted in challenges to nationally significant road and energy infrastructure.

Gethin is currently appointed as Chair of a public inquiry into an application made by the Saundersfoot Harbour Authority for a proposed harbour revision order. His inquiry experience includes acting on behalf of the successful party in a four-week inquiry, as junior counsel to Richard Wald KC, and as acting as sole counsel in a complex seven-day inquiry.

As a member of the Attorney General’s C Panel, Gethin frequently defends judicial reviews, statutory reviews and statutory appeals challenging planning inspectors’ appeal decisions in the High Court.

He is regularly instructed by developers, planning consultants, local authorities, and private clients to advise on all aspects of the planning process, including planning enforcement and planning appeals.

Notable recent instructions include:

• Saundersfoot Harbour Revision Order Inquiry (2025-2026): Chairing an inquiry into an application made by the Saundersfoot Harbour Authority for a proposed harbour revision order.
• Model Farm Planning Inquiry (2025-2026): Acting as sole counsel on behalf of a statutorily invited party, in a complex and high profile seven-day inquiry, in respect of a non-determination appeal of a hybrid planning application for the development of an industrial park on agricultural land. Representing the sole objecting party, opposing an applicant represented by King’s Counsel, Gethin cross-examined seven experts, across a diverse array of disciplines.
• R (on the application of Swire) v Canterbury City Council & BDW Homes Kent [2026] EWHC 478 (Admin): Acting on behalf of the Interested Party, as junior counsel led by Andrew Tabachnik KC, in the successful defence of a judicial review challenge to the grant of planning permission for new road infrastructure.
• R (on the application of Barclay) v Secretary of State & Gatwick Airport Limited [2026] EWHC 1556 (Admin): As junior counsel, led by Alex Goodman KC, acting on behalf of the Claimant in a judicial review of the grant of a development consent order for Gatwick Airport expansion, by its northern runway project.
• Roe Buck Holdings Ltd v Secretary of State [2026] EWHC 1737 (Admin): Acting on behalf of the Respondent, in a section 289 appeal of an enforcement notice, concerning ‘obvious alternatives’ and interpretation of planning policy.
• Isle of Anglesey County Council v Welsh Ministers (2026): Acted successfully on behalf of the Respondent, in a statutory challenge to the grant of permission for a solar farm, designated as a Development of National Significance.
• Enborne Parish Council v West Berkshire District Council (2025): Acted on behalf of the Claimant, as sole counsel, in a statutory challenge to the adoption of a local plan.
• R (on the application of Send Parish Council) v Guildford Borough Council (2024): Acted on behalf of the successful claimant in a judicial review of the grant of planning permission in respect of residential dwellings in the Corridor of the River Wey. The claim was conceded after permission was granted at an oral renewal hearing.
• R (on the application of Jennifer Dawes) v Secretary of State and Anor [2024] EWCA Civ 560: Acted on behalf of the Claimant, as junior counsel to Richard Harwood OBE KC, in a judicial review before the Court of Appeal challenging the second grant of development consent for the re-opening of Manston Airport in Kent, on climate change and need grounds. Gethin previously acted on behalf of objectors to the scheme, instructed by the Environmental Law Foundation, in respect to its climate change impacts. Gethin also acted as junior counsel to Paul Stinchcombe KC and Richard Wald KC in a successful judicial review challenging the first grant of the development consent order in 2021. For more information on the first claim, please see here.
• R (on the application of Transport Action Network Ltd) v Secretary of State and National Highways [2023] EWHC 860 (KB): Acted as junior counsel in a judicial review challenge to the grant of a development consent order for the A428 Road Improvement Scheme, on biodiversity and climate change grounds, led by Estelle Dehon KC.
• Ipswich Borough Council v Fairview Hotels (Ipswich) Ltd [2022] EWHC 2868 (KB): Acted on behalf of the local planning authorities in an injunction claim under section 187B of the Town and Country Planning Act 1990.
• R (on the application O’Shea) v Hertsmere BC and Civil Aviation Authority (2021): As sole counsel, acting on behalf of the Civil Aviation Authority, as an interested party to a judicial review challenge in respect of a certificate of lawful development issued to the operators of Elstree Aerodrome.

Gethin has a broad procurement practice, acting for both economic operators and contracting authorities across a diverse range of sectors.

He regularly acts in procurement challenges before the Administrative Court and the Technology and Construction Court, as both sole counsel and as part of counsel teams. He often advises on complex and novel issues arising at all stages of the procurement process, and under a range of procurement regimes.

Recent experience includes:

• Apasen Limited v London Borough of Tower Hamlets (2026): As junior counsel, led by Parishil Patel KC, defending both a judicial review challenge and TCC private law claim in respect of decisions regarding the direct award of interim contracts for domiciliary care.
• R (on the application of Cornwall Council) v Secretary of State for Housing, Communities and Local Government [2026] EWHC 1805 (Admin): As junior counsel, led by Joanne Clement KC and Tim Johnston, defending a judicial review claim challenging a decision to clawback a European Regional Development Fund grant due to breaches of procurement rules.
• Chigwell (London) Limited v Gateway Housing Association [2022] EWHC 3391 (TCC): As sole counsel, successfully obtaining summary judgment in a High Court claim brought seeking damages in respect of an abandonment of a procurement. Gethin acted on behalf of the contracting authority.
• Procurement challenge in defence sector: Assisted Parishil Patel KC in advising an economic operator. The claim concerned the application of the Defence and Security Public Contracts Regulations 2011 SI No 1848.
• Procurement challenge in healthcare sector: As sole counsel, advising an economic operator on the prospects of a challenge to the procurement of specialist led primary care orthodontic services, involving interpretation of the award criteria; equal treatment; non-discrimination; proportionality and transparency.
• Procurement challenge in social care sector: As sole counsel, advising the incumbent provider in respect of a challenge to the decision to award a contract to a newly established local authority trading company (relying on Teckal exemptions).
• Concessions contract: Advised on the scope of the Concession Contracts Regulations 2016.
• The Health Care Services (Provider Selection Regime) Regulations 2023: Advised on issues arising in respect of the application of the new Provider Selection Regime.

Gethin has a broad regulatory and disciplinary law practice. He regularly acts on behalf of regulatory bodies in judicial review claims, encompassing a diverse array of issues. He has also led the prosecution of disciplinary proceedings, as well advised upon various aspects of disciplinary processes, including appeals.

His experience includes:

• Acting in proceedings before the Solicitors Disciplinary Tribunal, and advising on Solicitors Regulation Authority (SRA) regulatory issues.
• Acting in proceedings before the Council for Licensed Conveyancers Adjudication Panel, including in a successful 5-day trial in a complex matter involving breaches of anti-money laundering rules (appearing as sole counsel against a KC).
• Acting on behalf of Social Work England in appeal and judicial review proceedings.
• Acting on behalf of the Professional Standards Authority for Health and Social Care.
• Acting on behalf of the Nursing and Midwifery Council.
• Acting on behalf of the Bar Standards Board in judicial review proceedings.
• Advising the Financial Ombudsman Service as consultant counsel.
• Advising the Office for Students as consultant counsel.
• Acting on behalf of the Civil Aviation Authority, in a successful strike out application of a claim in relation to a decision to provisionally suspend a pilot’s medical certificate in the High Court.

Gethin also gained experience of regulatory law whilst working in electoral law and misconduct in public office at the Law Commission.

Gethin has a commercial litigation practice with a particular focus on matters arising in regulated sectors, and raising public law or regulatory issues. He acts as both sole and junior counsel in the High Court, including in the Technology and Construction Court and Commercial Court, and in arbitral proceedings.

Gethin has significant experience of complex commercial trials and high-value disputes. He regularly advises on commercial matters involving statutory and regulatory regimes. He has particular experience of claims for damages pursuant to Article 1 of the First Protocol to the ECHR (A1P1).

Gethin has expertise in financial services regulatory matters, having previously been consultant counsel to the Financial Ombudsman Service. He has advised on a wide range of matters under the Financial Services and Markets Act 2000.

Gethin is currently instructed as a member of the legal team from 39 Essex Chambers offering legal advice and support to the Foskett Panel. Further information is available online here: www.foskettpanel.com.

Notable recent instructions include:

• Havant Biogas and ors v Ofgem (2025): Acted on behalf of Ofgem, in an A1P1 damages claim in the TCC for alleged loss of goodwill in respect of a biomethane production project, led by Jason Coppel KC and Angharad Parry. The claim settled shortly before trial.
• Meddyg Care (Criccieth) Limited v Betsi Cadwaladr University Local Health Board (2024): Acted, as junior counsel to Fenella Morris KC, in a breach of contract claim brought by a private care home provider against an NHS body. The private law claim raised issues concerning the NHS body’s statutory functions in setting care home services standard rates for private providers.
• R (on the application of Shawbrook Bank Ltd) v Financial Ombudsman Service Ltd; R. (on the application of Clydesdale Financial Services Ltd (t/a Barclays Partner Finance)) v Financial Ombudsman Service [2023] EWHC 1069 (Admin): As junior counsel, led by James Strachan KC, appeared on behalf of the successful Defendant in two joined cases challenged decisions of the Financial Ombudsman Service concerning “fractional ownership” timeshare schemes.
• Chigwell (London) Limited v Gateway Housing Association [2022] EWHC 3391 (TCC): As sole counsel, successfully obtaining summary judgment on behalf of a contracting authority, in respect of a High Court claim arising from the abandonment of a procurement exercise after the successful tenderer was notified.
• School Facility Management Ltd v Governing Body of Christ the King College [2021] EWHC 3066 (Comm): As sole counsel, acting in enforcement proceedings against a voluntary maintained school, in respect of a judgment debt arising from a commercial restitution claim, in the High Court.
• Avsar v Wilson James Ltd [2020] EWHC 3412 (QB): As sole counsel, successfully resisting an application for an interim injunction, both at first instance, and on appeal in the High Court.
• Arella Capital Ltd v TTG Capital Ltd (2021): As sole counsel, successfully obtaining summary judgment in respect of a breach of contract claim, arising in the context of a regulatory enquiry.
• Premier Roofline Installations Ltd v TK Products (Trade Counter) Ltd (2019): As sole counsel, successfully resisting an application to enforce an adjudicator’s decision in the High Court.

Gethin is a member of COMBAR.

Gethin has experience of international arbitration, and complex commercial trials. His recent instructions include acting as sole counsel in a commercial London Court of International Arbitration (LCIA) arbitration, and as junior counsel in an ad hoc arbitration in the energy sector.

Gethin recently acted in a complex, high value £1 billion 12-day arbitration trial (as junior counsel, led by Gordon Nardell KC, and with Fiona Whiteside). Gethin’s role included expert witness cross examination.

Gethin also has experience of arbitration enforcement action in the High Court, acting as sole counsel. Gethin acted in the enforcement of an interim SIAC award.

Gethin is also currently acting in an appeal against an arbitration award in the High Court, pursued under section 69 of the Arbitration Act 1996.

Notable recent instructions include:

• UNCITRAL arbitration (energy sector): As junior counsel, in a 12-day ad hoc arbitration trial of a £1 billion claim in the energy sector, led by Gordon Nardell KC, and with Fiona Whiteside. Gethin’s role included expert witness cross examination.
• LCIA arbitration (pharmaceutical sector): As sole counsel, acting in a commercial LCIA arbitration in the pharmaceutical sector.
• Enforcement of SIAC interim award (TCC): Acting in High Court enforcement of a SIAC emergency award granted during the course of a commercial arbitration.
• Section 69 appeal (TCC): Acting in a High Court appeal against an arbitral award, pursued under section 69 of the Arbitration Act 1996.

Gethin has a broad practice in financial services, banking and pensions law. Gethin has acted as consultant counsel to the Financial Ombudsman Service, where he advised on a wide range of issues under the Financial Services and Markets Act 2000. Gethin has also acted in several judicial review claims, on behalf of the Financial Ombudsman Service, as sole counsel.

Gethin is currently instructed as a member of the legal team from 39 Essex Chambers offering legal advice and support to the Foskett Panel. Further information is available online here: www.foskettpanel.com.

Notable recent instructions include:

• R (on the application of Shawbrook Bank Ltd) v Financial Ombudsman Service Ltd; R. (on the application of Clydesdale Financial Services Ltd (t/a Barclays Partner Finance)) v Financial Ombudsman Service [2023] EWHC 1069 (Admin): As junior counsel, led by James Strachan KC, appeared on behalf of the successful Defendant in two joined cases challenged decisions of the Financial Ombudsman Service concerning “fractional ownership” timeshare schemes.
• Stuart Binns & Associates v Financial Ombudsman Service [2021] EWHC 1620 (Admin): As sole counsel, successfully defending a judicial review claim.
• R (BMA, FDA, Prospect and PCS, GMB, Unite and ors) v Chancellor for the Exchequer (2020): As junior counsel, led by James Eadie KC, Daniel Stilitz KC, Simon Murray, and Joanne Clement in the judicial review challenges to the Public Sector Exit Regulations 2020.
• Pensions regulation: Assisting Katherine Apps, in advising as to the implications of R (on the application of Palestine Solidarity Campaign Ltd and another) v Secretary of State for Housing, Communities and Local Government [2020] UKSC 16, in respect of pensions regulation.
• PPI claims: Acting in payment protection insurance (PPI) claims on behalf of defendants.
• Agency: Advising as to apparent and ostensible agency.
• FSMA 2000: Advising as to the meaning of ‘credit’ and the scope of ‘financial accommodation’.

Gethin has experience of public inquiries, investigations and strategic reviews. His recent instructions include:

• West Midlands Fire and Rescue Authority Best Value Inspection: Gethin is currently appointed as an Assistant Inspector, with Anna Bicarregui, being led by Fenella Morris KC as the Lead Inspector.
• Harbour Revision Order Inquiry: Chairing an inquiry into an application made by the Saundersfoot Harbour Authority for a proposed harbour revision order.
• South Wales Fire and Rescue Service Culture Review: As junior counsel to Fenella Morris KC and Charlene Ashiru, assisting in respect of an independent cultural review.
• Independent Human Rights Act Review Panel: Advising the Independent Human Rights Act Review Panel, chaired by Sir Peter Gross.
• Infected Blood Inquiry: Acting as junior counsel to Charlie Corey-Wright KC by NHS Blood and Transplant, a core participant in the Infected Blood Inquiry.
• Advising the Windrush Lessons Learned Review.