De la Bedoyere replaces Jane O'Hara, who quit last month to go travelling, and was managing director of the Evening Standard between 2000 and 2002 but was forced out as part of a major shake-up at the London paper.
She joins at a controversial time for the radio industry, which is looking into replacing its outdated diary-keeping system with electronic monitoring systems.
Rajar is coming under pressure from TalkSPORT chief executive Kelvin MacKenzie, who is backing a rival system from Gfk Media, to switch to electronic testing.
De la Bedoyere left the Standard in September last year following speculation about a rift with Veronica Wadley, who replaced long-time editor Max Hastings. Prior to the Standard, she had spent 15 years at its parent Associated Newspapers.
During her career at Associated, De la Bedoyere was sales and marketing director and then advertisement director of the Mail on Sunday. She is a former deputy ad manager on Chat magazine, having begun her career at Haymarket Publishing working on Mims magazine.
She has experience in ratings following her time spent as a board member of the National Readership Survey between 1998 and 2000. Most recently, she has been working as a media consultant representing a range of media and leisure companies.
O'Hara had held the post of managing director of the radio audience measurement body for three-and-a-half years.
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