The actor Todd Carty, who played Mark Fowler in Eastenders, is being treated in hospital after collapsing on stage.
The Bill and EastEnders star found fame in Grange Hill
The 44-year-old passed-out at about 1630 GMT during a performance of The Business of Murder at The Gordon Craig Theatre in Stevenage, Hertfordshire.
His agent Derek Webster told BBC News 24 that Carty was "violently sick" on stage, but he was now recovering.
Mr Webster said it was still unclear what caused the collapse. The evening performance of the show was cancelled.
Mr Webster said: "It might have had something to do with an ear infection that Todd has been suffering from for a few days now - I can't actually confirm that.
'Awake and conscious'
"He did collapse on stage, he was violently sick. The theatre staff brought the curtain down, rushed him to the Stevenage hospital.
"He's undergoing tests, there's not much more that we can say, other than that he's well, he's awake and he's conscious and his wife is with him."
Carty has enjoyed a TV career lasting more than 30 years, with his big break coming as Tucker Jenkins in Grange Hill. From there he starred in the spin-off Tucker's Luck.
He joined EastEnders in 1988, replacing the original actor who played Mark Fowler who had committed suicide.
He was written out of the show in 2002, with the character leaving Albert Square so he did not put his family through seeing him die from an Aids-related illness.
He joined The Bill in 2003 as Pc Gabriel Kent, an officer who raped and murdered a colleague. He quit the show in 2005.