Sigsworth serves as the Chairman at Sigma Capital Group. He is also an Angel Investor. He also serves as Chaieman at Flexitricity. He spent over ten years as a main board director of FTSE 100 utility companies, the most recent being Scottish and Southern Energy (SSE). David is an Honorary Professor at Dundee University and active in promoting start-up companies that are developing technologies relating to clean energy and energy efficiency. He is also Chairman of the Scottish Environment Protection Agency (SEPA), Chairman of the Scottish Fuel Poverty Forum, Chairman of the Dundee Science Centre, Vice President of the Combined Heat and Power Association (CHPA), as well as a trustee of the think tank Sustainability First.