Broadcaster Andrew Marr is recovering in hospital after suffering a stroke, the BBC say.
The journalist and television presenter fell ill on Tuesday.
The BBC said in a statement: "Andrew Marr was taken ill yesterday and taken to hospital. The hospital confirmed he has had a stroke.
"His doctors say he is responding to treatment. His family have asked for their privacy to be respected as he recovers.
"We will continue to broadcast The Andrew Marr Show and Radio 4's Start The Week with guest presenters in his absence.
"His colleagues and the whole BBC wish him a speedy recovery."
Many of Marr's colleagues in the media took to Twitter to express their sympathy.
Fellow BBC politics presenter Andrew Neil wrote: "Very distressed to hear news about Andrew Marr. Best wishes for full and speedy recovery."
Guardian columnist Polly Toynbee tweeted: "Andrew Marr, renaissance man, polymath, wise commentator, painter, runner, brilliant cook - and ace editor. Get well soon. Needed in public life."
Former Tory MP Louise Mensch said: "Joining in the chorus of well-wishers for Andrew #Marr. Hope he has a speedy and full recovery."