Newsreader George Alagiah has been diagnosed with bowel cancer and is to be off air for the near future while he receives treatment, the BBC has said.
The 58-year-old, who has been a familiar figure on TV news bulletins for many years, is said to be "optimistic" about a positive outcome.
The Sri Lanka-born journalist has been the face of BBC1's News At Six since 2007.
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In a statement the BBC said: "He is grateful for all the good wishes he has received thus far and is optimistic for a positive outcome. George asks that he and his family are given the space and privacy they require whilst he recovers.
"Our thoughts are with him and his family and we send them our very best wishes during this time. Until such time as George is well enough to return to work the BBC News at Six and GMT on BBC World News will be presented as usual by familiar faces from BBC News."