Veteran stand-up comedian Ian Cognito has died on-stage during a performance.
The comic is said to have “sat on a chair and laid back for five minutes” during his show at the The Atic bar in Bicester on Thursday.
Audience members told the BBC they thought his silence was “part of the act” and had continued to laugh, unaware he had fallen ill.
South Central Ambulance Service confirmed Cognito was pronounced dead at the scene.
John Ostojak attended the gig at the Lone Wolf Comedy Club with a friend, and said the comic “did a really good set”.
“Only 10 minutes before he sat down he joked about having a stroke,” Mr Ostojak said.
“He said, ‘imagine having a stroke and waking up speaking Welsh’.”
When Cognito sat down towards the end of his set, Mr Ostojak said: “We thought it was part of the act.
“We came out feeling really sick, we just sat there for five minutes watching him, laughing at him.”
The compere eventually approached the stage, and got someone to call an ambulance.
Staff attempted to perform chest compressions and asked the audience to leave while they waited for help to arrive.
Cognito, whose real name was Paul Barbieri, was born in London in the late 1950s.
He had been performing since the mid-1980s, and was well-respected on the comedy circuit.
Fellow comedians have paid tribute, describing him as a “proper comic” and praising his support for up-and-coming acts.
Eight Out Of Ten Cats presenter Jimmy Carr paid tribute to Cognito, saying: “I’ll never forget his kindness when I started out…”
Comedian and columnist Mark Steel said the comic was “a difficult awkward hilarious troubled brilliant sort, a proper comic”.
BBC Radio 4 Extra’s comedy club presenter Arthur Smith said Cognito was “hugely admired by his fellow comics”.
Rufus Hound said on Twitter: “we have lost one of the greats”.
Shappi Khorsandi said it was “such a sad shock”, and Cognito was “one of the people who made this job brilliant”.
Mitch Benn, known for his appearances on The Now Show, said he had known Cognito for 25 years and when he saw him last month he “looked better than I’d seen him in years”.
Birmingham’s Glee Club comedy venue also paid tribute.
Cognito, who was based in Bristol, won the Time Out Award for stand-up comedy in 1999.