Presenter Carol Vorderman has decided to step down from Channel 4's popular daytime game show "Countdown" after nearly 26 years, her agent said on Friday.
She will appear on the words and numbers quiz for the last time at the end of the year.
No reason was given for her departure.
Her manager John Miles said she was extremely sad to be leaving.
"It was a difficult decision because she loves Countdown dearly and always has," he said in a statement.
"The contestants, viewers and crew are like family to her."
She joined the programme at its launch and has chosen more than 70,000 letters for the contestants during nearly 5,000 programmes.
Vorderman first appeared alongside Richard Whiteley and considered quitting when he died in 2005 but she continued and became co-host with Des Lynam and then Des O'Connor, turning down the offer of taking over as host, Miles said.
The Cambridge graduate broke the mould of the game show hostess, showing her intellectual agility by carrying out fast and accurate calculations, and becoming one of the highest-paid women presenters.
She was the first woman to appear on Channel 4 when it launched in November 1982 and Countdown's popularity has endured through the decades, being voted Channel 4's best show of all time by viewers in a 2003 poll published in the Radio Times.
Kevin Lygo, Channel 4's director of television and content, said: "We are extremely sorry to see Carol leave. She has made an enormous contribution to the success of Countdown. We hope to work with her again on other projects."
John Whiston, director of ITV Productions who make the show under the Granada name for Channel 4 said Vorderman had been the "heart and soul" of the programme.
"This is truly the end of an era.
"Her fans have loved her cheery presence at the numbers board along with her amazing mathematical skills."
Des O'Connor announced earlier this week that he was to step down in November.
Replacements have yet to be announced.
It was unclear what her plans are but Vorderman has frequently appeared on other television shows and has launched brain-training games.
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