John is a Law graduate of Trinity College, Dublin and has a Masters in Law from St John’s College, Cambridge. He practiced in EU and Competition Law in Brussels with Clifford Chance and then established the EU and Competition Law practice in Arthur Cox in Dublin and subsequently in Belfast. He was Head of the firm’s practice for 25 years before establishing his own practice in 2016. He was subsequently called as a Senior Counsel in light of his practice in EU and Competition Law.

John is regarded as one of the leading practitioners in his practice areas on the island of Ireland. He received “outstanding feedback from clients and peers” in the 2025 Chambers Europe review of EU and Competition Lawyers in Ireland.