Gavin and Stacy star Mathew Horne will decide today whether to carry on with a West End play after collapsing on stage from apparent exhaustion.
He fell to the floor 15 minutes into the second half of yesterday's matinee show of Entertaining Mr Sloane at Trafalgar Studios theatre.
The actor was treated on stage before the manager asked the audience to leave.
Horne's spokesman told the BBC that he was taken to hospital but released afterwards, with a decision being made today whether to continue with the show.
The spokesman said Horne collapsed after working flat out for three months, the BBC added.
His co-star in Entertaining Mr Sloane, Imelda Staunton, has also pulled out of the performance after becoming unwell, a spokesman for the Trafalgar Studios theatre said.
Understudies have replaced the two leading lights in the play written in the 1960s by Joe Orton.
Fellow performer Simon Paisley Day called out for any doctors in the house to come forward after Horne collapsed, with the actor lying on the stage for 10 minutes before paramedics arrived.
John Rigby, a BBC producer in the audience, told the BBC that Horne seemed "absolutely fine" during the first half of the Joe Orton play but that there was a delay after the interval.
It was announced the play would resume in three minutes, but a further 10 minutes elapsed before the actors took to the stage.
Mr Rigby said the audience seemed to believe Horne's collapse was part of the show until fellow actor Paisley Day called out: "I think something has gone wrong, is there a doctor in the house?"
One audience member went to help while another called out for someone to dial 999. An actor on stage replied: "Don't worry, it's been done".
Horne recently starred in Lesbian Vampire Killers with James Corden.
The busy pair also have a sketch show on BBC3 called Horne and Corden, which has received mixed reviews.
The Bafta-winning duo became household names after the phenomenal success of the BBC show Gavin and Stacey.
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