Simon is a professional arbitrator and mediator, handling a wide variety of international maritime cases. His arbitration practice involves deciding disputes arising under time and voyage charters, bills of lading contracts, sale and purchase contracts, shipbuilding contracts, contracts for the sale of goods, marine insurance policies, and agency and commission agreements. His mediation practice involves assisting parties reach a negotiated settlement in similar types of dispute.

Simon was the Honorary Secretary of the London Maritime Arbitrators Association for over four years. In this capacity, he advised on and lectured about a wide range of issues which arise under the Arbitration Act 1996. He is a barrister with over thirty years experience of arbitrating and litigating shipping cases. He was counsel in a number of leading shipping or arbitration cases. He appeared as counsel in a number of wreck inquiries. He practiced from what is now Quadrant Chambers and served as the deputy head of those chambers for a number of years. He is now a door tenant of those chambers.

Before qualifying at the bar, he had 5 years experience in the shipbuilding industry both in the UK and overseas. After retiring from practice, he was appointed chairman of a shipping group, and was responsible for instituting a programme of rationalization of the group. He has over 11 years of judicial experience as a recorder of the crown court, as deputy admiralty registrar, and an assistant boundary commissioner. He is a trustee of a number of charities including the Incorporated Council of Law Reporting. He is the general editor of Marsden - Collisions at Sea. He is a member of the Baltic Exchange. He is also a visiting professor of law at Newcastle University.