Countdown host Richard Whiteley is to miss his first show in 23 years as he continues to recover from pneumonia.
Whiteley has presented Countdown for 23 years
Whiteley, 61 and from Ilkley, was admitted to intensive care at Bradford Royal Infirmary on 6 May.
Producers of the Channel 4 teatime show have said a series of guests will present the programme until Whiteley is well enough to return.
The presenter, who has hosted the show since 1982, is said to be "recovering slowly" from his illness.
'Surprise for viewers'
A Channel 4 spokeswoman said the identity of the celebrity presenters has not yet been identified.
She said: "We want to keep it a surprise for our viewers."
All the personalities will be people who have previously appeared on the show and will co-host it with Carol Vorderman.
Whiteley is still on screen as episodes are pre-recorded, although those shows run out in July.
A Yorkshire Television spokeswoman said: "All his colleagues and friends wish him well and hope he will soon be back behind the Countdown desk."
Whiteley has been presenting Countdown since it was the first show to be broadcast on the fledgling Channel 4.
It was originally planned to run for five weeks but now has regular viewing figures of four million.
Last November Whiteley was honoured with an OBE from the Queen, who is said to be a fan, as was the late Queen Mother.