Gwion is a leading barrister in the areas of planning, environmental and public law and took silk after only 16 years in practice. Described by clients as a “force of nature”, he has an established reputation as a litigator, with solicitors consistently commending him for his “brilliant” advocacy, “fearsome” cross-examination and being “a pleasure to work with” (Chambers & Partners).

Gwion regularly appears in high-profile litigation in his areas of expertise. He is most widely known for acting for the successful party in the Hillside Parks litigation about multiple planning permissions for the same land, arguably the most significant planning case to reach the Supreme Court in the last 20 years.

Gwion’s practice also received national attention when a former Secretary of State conceded in the High Court that he had acted with apparent bias when granting planning permission for the Westferry Printworks redevelopment in east London. Gwion acted for the successful party, Tower Hamlets Council.

Gwion’s clients are diverse. He purposely retains a broad client base in both the private and public sectors so that his clients benefit from his understanding of how different parties are likely to approach a problem.

Planning inquiries are a major part of his practice. Gwion has extensive experience of acting for developers in appeals raising difficult issues in relation to design, architectural quality, cultural heritage and viability, especially in and around London. For further details of these cases, please click on the ‘Planning’ tab above.

Highly technical planning and environmental appeals where experts disagree about environmental impacts also feature heavily in Gwion’s practice given his “forensic” approach to evidence and “ability to rapidly absorb, filter and distil” technical material (Chambers & Partners).

Gwion regularly acts for leading national housebuilders across England and Wales, including Persimmon, William Davis and Bloor, and has achieved many successful outcomes for boutique residential developers in both urban and rural locations.

Since taking silk, Gwion has acquired further expertise in promoting market-leading retirement schemes at appeal. Current clients include KYN (a dementia care home and research centre in Cambridge) and Elysian Residences.

He also works frequently with clients from the retail sector. Recent successes include a series of judicial reviews for the Midcounties Co-operative to overturn planning permissions granted to a competitor, and defeating a rival developer’s proposal to demolish the Homebase store in Saffron Walden.

In addition to acting in planning appeals, Gwion has considerable experience of the development consent process for large infrastructure projects, having acted for Natural Resources Wales, the Welsh environmental body, in all the high-profile Welsh DCO hearings of the last 10 years (including the proposal for a new nuclear power station on the Wylfa site on Anglesey; the Awel y Môr offshore windfarm near to the north Wales coast; and the proposal for the world’s first man-made, energy-generating tidal lagoon at Swansea Bay).

Gwion enjoys long-standing relationships with many public bodies in England and Wales, building on his previous experience as a member of both the Attorney-General’s ‘A’ Panel of Counsel, and the Welsh Government’s Panel of Junior Counsel, before taking silk. He is regularly instructed by the Environment Agency in judicial reviews and environmental permitting appeals and is currently leading the Agency’s climate change officials in defending the first tranche of civil penalties imposed on aircraft operators under the UK’s new Greenhouse Gas Emissions Trading Scheme.

Gwion’s regular local authority clients include (to name only a few) Hounslow Council, Tower Hamlets Council, Chichester District Council, Torbay Council, Mid Sussex District Council, South Hams District Council and the South Downs National Park. In the recent directories, a local authority client praised Gwion for his consistently “punchy” and “succinct” written advice that makes “complicated cases look straightforward despite difficult points” (Chambers & Partners). His work for local authorities spans the full range of their functions, including education, elections and ethical standards.

Gwion is based in London but welcomes instructions from all parts of the United Kingdom and from international clients. He is Welsh-English bilingual.

• LLM, New York University, specializing in international human rights, language rights and the interface between law and security (2003-04)

• Certified upper-intermediate Italian speaker (University of Siena, 2011, CILS)

Scholarships

• Former US-UK Fulbright Scholar

• Scholar, Jesus College, Oxford: BA, Jurisprudence and BCL (First Class) (1998-2002)

• Visiting Scholar in Language Rights, European University Institute, Florence (2004)

• Bedingfield Scholar, Gray's Inn (2004)

Awards

• Shortlisted for the Legal 500 UK Bar Awards 2023 Planning and Land Use 'Silk of the Year'

• Honorary Fellow, Bangor University, Wales, for services to law (2017)

• Best Breakthrough, BAFTA Wales Television Awards (2013) for presenting a television documentary on the Welsh language

• Welson Prize, Most Promising Law Student (Jesus College, Oxford, 2003)

• Winner, Oxford-Cambridge Intervarsity Mooting Competition (2001)

Memberships

• Trustee, American School in London (2023-ongoing)

• Welsh Language Partnership Council, Welsh Government (2017-2020