Duncan was an MI6 agent in the 21st century. He was a close ally of Grace Holloway and later, the Eighth Doctor.
Duncan assisted Grace in her experiments on humans and Time Lords. He arrested the Doctor[which?] and Izzy Sinclair until he realised the Doctor was a Time Lord and a close friend of Grace's. He was killed whilst trying to stop the Master and Donald Stark. (COMIC: The Fallen)