David Barnett spent all his business life at Cazenove, at the time the City's major UK Independent securities firm. He was a partner for 29 years, including being finance partner and second senior partner, before his retirement in 2001. He has continuing roles as a Governor of Reed's School, where he is Chairman of the Risk Management Committee, and he is Chairman of the JPMorgan Cazenove Pension Scheme Trustees. He is a Patron or Trustee of a number of other charrities including Independent Age. He is a Liveryman of the Goldsmiths' Company and a member of the Investment Committee. Most of the organisations with which he is involved have Finance, Investment and Pensions Committees on which he serves.

David has been a Trustee of Independent Age since 2003. He is a member of the Finance and Audit Committee, the Investment Subgroup, the Branding and Ethos Steering Committee and the Pensions Committee, of which he is the Chairman.