He will be the station's fifth chief executive and replaces Mark Thompson, who left Channel 4 to become the new director-general of the BBC.
Duncan, with his marketing background, is a surprising choice. Among the names thought in the frame for the job were Dawn Airey, the managing director of Sky Networks, Simon Shaps, the chief executive of Granada, Peter Fincham, the chief executive of Talkback Thames, and Jana Bennett, the director of television at the BBC.
Duncan joined the BBC three years ago from Unilever, where he was in charge of the company's yellow fats brands. In 2002, he became the chairman of Freeview, the digital terrestrial platform part-funded by the BBC.
Commenting on Duncan's appointment, Luke Johnson, the chairman of Channel 4, said: "He has a strong understanding of the public-service ethos in a modern broadcasting world. He has worked at the top of the BBC for the past three years, covering a range of strategic issues. He has a superb track record of innovation as a key architect of Freeview, perhaps the most successful media launch ever."
Duncan added: "Channel 4 has an excellent track record over the past 20 years or so, and has established a strong reputation with its audiences.
At the same time, it has managed to punch well above its weight. The heart of my job working at Channel 4 over the next few years is to ensure this continues."
- Newsmaker, p12.