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Barristers

Mark O\'Brien O\'Reilly

Mark O\'Brien O\'Reilly

Position

Mark is a leading barrister with a growing reputation for experience and skill beyond his call. He is ranked as one of the top junior planning barristers in the country by Planning Magazine’s Planning Law Survey 2024 (and also holds a ranking as one of the top ten planning barristers under the age of 35 with Planning Magazine noting he was the highest new entrant on that list and his particular injunction expertise). The High Court has described his submissions as “concise and well-structured”. Clients have praised him as “commercial” and “user friendly”.

Mark regularly appears at planning inquiries concerning a broad range of developments, with a particular expertise in residential schemes, tall buildings and renewable energy projects. He has recently successfully promoted a 49.9MW solar farm scheme at inquiry and acted in the Court of Appeal on behalf of the Interested Party defending the grant of planning permission for hydrocarbon exploration and appraisal within an AONB. Other recent significant cases include successfully defending the DCO for Manston Airport in both the High Court and the Court of Appeal, numerous successful applications in the High Court for planning injunctions and representing the Royal Borough of Greenwich in the Mast Quay Enforcement Notice appeal having advised the Council throughout the enforcement investigation (a 204 unit residential development consisting of two tall buildings beside the River Thames).

Mark has a strong and busy practice across all of Chambers’ practice areas, with a particular expertise in planning, infrastructure and compulsory purchase/compensation work. Mark has a strong reputation as an advocate and, unusually for his year of call, regularly appears in the High Court, including as sole counsel and against leading KCs. His advocacy experience, including cross-examining in the Old Bailey, means he is generally instructed against more senior counsel, including KCs. He appears before a broad range of courts, tribunals and planning inquiries. He is also regularly instructed as junior counsel to other members of Chambers, including leading silks. He has a broad range of clients ranging from developers, renewable energy companies and landowners to local residents. He has extensive experience of acting for, and advising, central government and local government (and has acted for many London boroughs).

Mark is in demand for his planning expertise, and regularly acts for both appellants and local planning authorities in planning inquiries. He is also noted for his strong experience of injunctions, including section 187B injunctions, and is regularly called upon, often urgently, to advise upon and obtain High Court injunctions (and has acted in many of the recent reported cases concerning section 187B injunctions).

During his pupillage, Mark was awarded the Reid Scholarship by Gray's Inn, a Senior Scholarship for Pupillage, which is the Inn's most prestigious scholarship and awarded to a pupil barrister of exceptional merit. He is a First Class Honours graduate of University College Dublin (BCL Law with History) and the University of Cambridge (LLM). Mark was called to the Bar of England and Wales in 2021 and the Bar of Ireland in July 2023.

Mark welcomes instructions across all of Chambers' practice areas, with a particular interest in planning, public and compulsory purchase/compensation as well as licensing and environmental law.

Away from his busy practice, Mark owns and breeds racehorses. He is well placed, therefore, to advise racing yards, stud farms and racecourses as well as a broad range of equestrian facilities on the planning issues they face. He also enjoys travelling and volunteering.

Career

Awarded the Reid Scholarship by Gray's Inn, a Senior Scholarship for Pupillage which is the Inn's most prestigious scholarship and awarded to a pupil barrister of exceptional merit Elected by the Governing Body of Queen’s College, Cambridge to a Foundation Scholarship Awarded a full scholarship plus maintenance (the Snowdon Cambridge Scholarship 2020) by the Cambridge Trust to undertake an LLM (Master of Law) at the University of Cambridge The Baroness Hale of Richmond BPTC Scholarship 2019, awarded by The Honourable Society of Gray's Inn, is the Inn’s newest and most prestigious scholarship. It is awarded to candidates of exceptional merit The BPTC Advocacy Scholarship 2019 is awarded by BPP University Law School to those who demonstrate an outstanding aptitude for advocacy The Career Commitment Scholarship 2019 is awarded by BPP University Law School to those who are considered to be the most promising future legal professionals The Jomati Foundation Bursary 2019, awarded by the Jomati Foundation, assists students of high academic ability with the costs of qualifying as a barrister The Hebe Plunkett Award 2019, awarded by The Honourable Society of Gray's Inn Irish Law Student of the Year 2019 awarded at the Irish National Law Awards in recognition of academic, professional and personal achievements The Gold Medal for Mooting 2017 which is awarded by the University College Dublin Law Society to the student most successful in mooting in the previous academic year Certificate in Work Related Learning (Commercial Law in the City of London) 2017 awarded by the University College Dublin Career Development Centre

Memberships

Constitutional & Administrative Law Bar Association (ALBA) UK Environmental Law Association (UKELA) London Irish Lawyers Association The Planning and Environmental Bar Association (PEBA) The Ireland Funds (Great Britain) Compulsory Purchase Association (CPA) The London Irish Construction Network The NAtional Infrastructure Planning Association (NIPA)

Education

BCL Law with History 2019, University College Dublin, First Class Honours Bar Professional Training Course, September 2019 – August 2020, BPP University Law School, Outstanding LLM (Master of Law), University of Cambridge, October 2020 – June 2021, First Class Honours. Papers included International Environmental Law and Information Law
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