John trained with Eversheds in Manchester qualifying in 1993 and on qualification remained with the firm as a solicitor where he worked in the corporate, commercial and intellectual property teams including in-house placements with Zeneca and Granada Television before leaving in 2007 to become a Partner at Halliwells in Manchester. In 2001 John joined offshore law firm Appleby in Bermuda working as Counsel to the firm in the corporate insurance and reinsurance department where he was responsible for acting for US private equity investment in new Bermuda-based reinsurance companies in the wake of the 9/11 attacks and was involved in the subsequent listing of those new reinsurance companies on NYSE. 

John co-founded McMahon McKay in Belfast in 2016 and has developed a wide-ranging practice encompassing renewable energy, carbon reduction and sequestration, logistics, healthcare, leisure and hospitality, aerospace and transport. John is recognised in the Legal 500 for M&A. John heads the Corporate Commercial team in the Northern Ireland office.