Leslie qualified as a Chartered Accountant with Coopers & Lybrand in Jersey. He later left to become the Financial Controller of Barclay Trust International Limited in 1974 and in 1977 he left to establish his own Chartered Accountancy practice and to establish a trust company with two other partners.
In 1987 this trust company was sold to Jardine Matheson and Leslie became the Chief Executive of Jardine Matheson’s international trust operations until 1994. In 1994 he left to establish Channel House Financial Services Group of which he was Executive Chairman until its sale to Capita Group Plc in September 2005. Leslie was Executive Chairman and Head of Private Client of Capita Fiduciary Group Limited until February 2009 when he joined LGL Trustees.