Simon spent the majority of his career at Robert Fleming Holdings and subsequently at Fleming Family & Partners where he focused mainly on Private Equity. He started his career at a California based Venture Capital Manager before joining the Investment team of Flemings in New York .

In 2000, he joined Fleming Family & Partners Asset Management and was responsible for US$500 million of Private Equity investments. Since leaving FF&P in 2013, Simon devotes the majority of his time to 54 Capital and a US family office, where he serves as Chairman of the Investment Committee. He is also a Director of Foresight Venture Capital Trust 4.