He is a former lawyer and was a partner of Freshfields Bruckhaus Deringer, where he founded and managed the Brussels office and led the Global Competition Practice. Prior to Freshfields, John worked as a case officer in the European Commission's Directorate-General for Competition.
John was voted Antitrust Lawyer of the Year 2016 and received an Antitrust Lifetime Achievement Award in 2019 both from Global Competition Review. He is a vice-chair of the International Policy Committee of the American Bar Association.