Lygo quit Five in July to join Channel 4, where he became director of television replacing Tim Gardam who left after five years at the broadcaster.
Chambers takes up his new role immediately. He joined Five in 2001 from Channel 4, where he was editor of science and was responsible for commissioning programmes such as 'Secrets of the Dead', 'Scrapheap Challenge' and 'The Private Lives of Pharoahs' and was jointly responsible for the first series of 'Big Brother'.
In his two years at Five as factual controller, he has commissioned 'Britain's Worst Driver', 'Fifth Gear' and 'Britain's Finest' among others.
Chambers said he was delighted with the promotion and called the programming team he would be working with "the best programming team working in British broadcasting".
"Five is a great success story and I look forward to building on the channel's ever-growing reputation as a home of creativity and innovation," he said.
Joining him on the team will be Jeff Ford, Five's director of acquisitions, who has been promoted to the newly created role of managing editor. Ford will retain his existing responsibilities, as well as handle the programming department's finances, staff training and development, and internal communications. He will also deputise for Chambers.
The appointments are the first to be made by new Five CEO Jane Lighting, who replaced Dawn Airey in February. After a low-profile start at the channel, Lighting was forced into the spotlight after Lygo quit to go to Channel 4 and Lighting took over his responsibilities in the interim.
Lighting said: "It's a great tribute to the quality and calibre of the whole programming department that we've been able to make two such important appointments from within.
"Dan has exceptional ability and has been an important part of the Five creative team that has commissioned so successfully for us, while Jeff's experience and judgment of acquired programming has made him pre-eminent in his field."
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