Duncan was formerly Operations Director for the GB Electricity and Gas Transmission Grids and Chief Sustainability Officer for National Grid Group. In these roles, he oversaw the development of the British Power Grid as it became the fastest decarbonizing grid in the G20, saw the first coal-free operation of the GB electricity system, and set a strategy for zero carbon operation by 2025. Alongside this, Duncan worked closely with a range of TSOs across the globe in the run-up to COP26 in Glasgow and was named one of the Global Top 100 Sustainability leaders by Sustainability Magazine.