Experience

Sion advises a wide range of clients in relation to all aspects of general litigation. He deals mostly with contentious issues and his clients include individuals, companies as well as well-known State and charitable organisations.

Sion represent clients in the District, Circuit and High Courts (including the Commercial Court) and often appears as an advocate. He also represents clients before Tribunals to include the Employment Appeals Tribunal and Professional Misconduct Tribunals. Sion also has experience in acting for clients who have agreed to resolve their disputes by way of arbitration as an alternative to proceedings being litigated through the Courts.

Sion also acts for a number of religious organisations and is considered to be a leading practitioner in the area of abuse claims, having acted for his clients in a number of high profile cases.

Sion has an interest in Environmental and Planning Law and acts for a number of State bodies in this area. He has extensive experience in acting for State bodies in CPO oral hearings before An Bord Pleanála.

Recent Testimonials

‘For me, O’Flynn Exhams stands out for its client-first approach. My experience with Sion Williams has been excellent. I have found him extremely approachable, knowledgeable, friendly, and always reassuring. His professionalism and courteous manner truly sets him apart.’ – Legal 500 (2025)

‘I found Sion Williams to always be available, or returns calls promptly, and is extremely knowledgeable. I highly value his personalised service and for me this sets them apart from competitors by fostering strong, collaborative relationships.’- Legal 500 (2025)

‘Sion Williams has repeatedly demonstrated an extraordinary willingness to go the extra mile for our business, making himself available outside of traditional working hours whenever needed. His proactive assistance, especially during time-sensitive or urgent matters, gives us the peace of mind that we have a trusted adviser who is always looking out for our interests.’ – Legal 500 (2025)

‘Sion Williams would be my stand out individual, always available, a superb communicator and consummate expert.’ – Legal 500 (2023)