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John Humphrys will step down as host of long-running BBC quiz Mastermind at the end of the current series.
Writing in the Daily Mail, Humphrys, 77, said he would be giving up the role in March, after 18 years.
"Now, after more than 750 shows, it really is time to finish," he said in a nod to the show's catchphrase.
Humphrys, who took on the quizmaster role in 2003, said he did not envy his successor - adding Mastermind was a show you tinkered with "at your peril".
The BBC said it wanted to thank Humphrys for his work on the programme. "He has been a first class presenter and we look forward to working with him on other projects in the future," a spokesman added.
There is currently no word on who might follow in Humphrys' footsteps.
"When the present series comes to an end in March there will be someone else in the chair," the former Today programme presenter wrote in his newspaper column.
"I wish my successor well - but I'm not sure I envy them, whoever 'they' may be.
"What are the odds on the first female?" he added.
Humphrys said when he took on the role of Mastermind host in 2003, the BBC stipulated that he must retain predecessor Magnus Magnusson's much-mimicked coda: "I've started, so I'll finish."
"Mastermind is one of those programmes you tinker with at your peril," he wrote in Saturday's column. "Allow a contender to choose a light-hearted subject and the cry goes out: 'Dumbing down!' Change the format even slightly and you are 'sexing up'."
Magnusson was the first host of Mastermind, which debuted on BBC One in 1972.
The show features four contenders who each answer questions on a specialist subject of their choice against the clock, followed by a series of general knowledge questions. There are no cash prizes, just kudos.
The show, which originally aired in a late night slot amid fears it was too highbrow, has become a national institution - and is famous for its black leather chair, in which the contestant sits, and ominous theme tune, aptly titled Approaching Menace.
Broadcaster Humphrys built a reputation as a tenacious interrogator of politicians on BBC Radio 4's Today show, stepping down as a presenter on the show in September 2019, after 32 years.
He has since taken on a presenting role on Classic FM.