Stewart is a Chartered Accountant. He was the founder and Chairman of Newton Investment Management from 1977-2002 and in 2003, he became the Chairman and founder partner of The Real Return Group Ltd, which subsequently merged with Veritas Investment AG in 2004. Having previously served as Chairman and President, Stewart currently sits on the Board of Veritas Investment Partners Ltd. Stewart was a Non-Executive Director of HSBC Holdings plc from 2002-2008, a Council Member of Imperial College and the Chairman of the committee advising the Council on the Endowment Fund from 2007 to 2015 and a Director of The Herald Investment Trust plc from 2012 to 2015. He formerly sat on the board of VenCap (Channel Islands) Ltd, the Investment Committee of The Wellcome Trust and the Investment Board of Cambridge University. Stewart is an active investor in private healthcare and technology companies in the UK, and also President of The National Trust for Jersey.