He has worked for the London law firm Bircham Dyson Bell since 1978, and has been a partner since 1983. He is currently head of the firm's Individuals Group, specializing in charities, tax planning, investment property for charities and the resolution of potentially contentious issues arising out of wills, trusts and co-ownership of property for charities and private clients. Simon is a member of the Charity Law Association and the Association of Contentious Trust and Probate Practitioners, and he sits on the advisory board of the European Association for Planning Giving. Simon has helped to pioneer the development of real property investment pooling schemes for charities and advised in the creation of the Absolute Return Trust for Charities, the first common investment fund of hedge funds.