Duncan is Chief Executive of Sustainable Aviation, working with industry and government to lead UK aviation to a sustainable future - reaching net zero by 2050 and effectively managing the noise issues around airports.

Prior to this, he was a Partner at Brunswick from 2019 to 2024, leading teams to support international clients with corporate reputation, public policy, and competition issues. From 2016 to 2019, Duncan was Chief of Staff and Special Advisor to former Chancellor Rt Hon Phillip Hammond MP where he provided advice on fiscal policy, Brexit, financial services and transport issues, among other things. Duncan also served as a Special Advisor to Phillip Hammond as the Secretary of State for Foreign and Commonwealth Affairs, and was campaign director and office manager for Andrea Leadsom MP from 2010 to 2015.

Before that, Duncan was chief executive at MCA Ltd, a management consulting firm, providing managerial and strategic advice to large companies and has also worked in European equity strategy for Credit Suisse and JPMorgan Chase in London, and consulted at the World Bank and KPMG in Washington, D.C. Duncan is a Non-Executive Director of the National Citizen Service Trust.