Carol Vorderman is to step down from her role in the long-running Channel 4 gameshow 'Countdown', her manager said tonight.
The presenter, who has been with the programme for 26 years, was said to be "extremely sad".
Her decision follows the announcement on Wednesday that Des O'Connor, the 76-year-old current host of 'Countdown', is also to quit the show.
Vorderman, 47, has been with the show since it began in 1982 and was the first woman to appear on Channel 4.
Ever since she has been a regular part of 'Countdown', coming into her own as the show's resident maths expert.
She even became something of an unexpected sex symbol among male fans, many of whom viewed her as a thinking man's pin-up.
For more than 20 years she acted as a foil to the show's main presenter Richard Whiteley, who died in 2005.
In today's statement, her manager said she had considered quitting following his death, but eventually agreed to continue alongside first Des Lynam and then Des O'Connor.
Earlier this week, O'Connor announced his decision to step down from presenting the weekday show.
It led to speculation over the show's future and the role of the programme's other regulars.
John Miles, Vorderman's manager, said today that stepping down had been a "difficult" decision for her.
He added: "Carol was the first woman on Channel 4 and she is enormously grateful to have had 26 wonderful years and nearly 5,000 shows on Countdown.
"She wants to thank all of the crew, the thousands of contestants who have played the game and the millions of Countdown viewers for whom she has the greatest respect."
Aside from being a TV presenter, Vorderman has developed a writing career as both a newspaper columnist and a best-selling author of Detox books.
Vorderman is due to step down from 'Countdown' at the end of the year.
Fellow regular on the show, lexicographer Susie Dent, said: "It's the end of an era for Countdown, and it's the end of an era for me - Carol has been my colleague, my mentor, and my friend for over 15 years.
"She and Richard together made one of the strongest and enduring shows television has ever seen, and also built one of the closest teams. For the programme to lose someone with Carol's astonishing ability, vigour, and passion, is devastating."
It is believed Vorderman's decision was motivated by a desire not to go through having to bond with yet another new co-presenter.
Mr Miles said: "She didn't think she could go through that process again. She just feels that it is time to leave."
Kevin Lygo, Channel 4's director of television and content said tonight: "We are extremely sorry to see Carol leave. She was the first woman on Channel 4 and has made an enormous contribution to the success of Countdown over the last twenty five years.
"We hope to work with her again on other projects."