Brian Blessed returned to the stage just 20 minutes after collapsing during a production of King Lear, according to reports.
The booming-voiced 78-year-old had begun to deliver his opening lines in the Shakespearean tragedy when he apparently fainted and fell from a raised platform.
Daily Mail critic Quentin Letts reported that fellow actor Noel White said: "Ladies and gentlemen, this is not part of the play. Is there a doctor in the house?"
A doctor from Holy Trinity Church in Guildford, Surrey, who was at Monday night's performance attended to the ex-Z Cars actor on stage in front of the audience, including his daughter Rosalind.
The veteran actor - whose career in television, film and stage has spanned six decades - returned 20 minutes later after being clapped off by the audience, Letts reported.
In his review, the Daily Mail's critic added: "After being given a cup of sweetened tea, he returned to the stage after 20 minutes to apologise to the final-preview audience for the interruption."
Brian reportedly said: "I feel such an idiot and am not in the habit of doing this, but I have little fibrillation."
At the curtain call, as some other cast members were said to be in tears, Brian patted his heart and gave a thumbs up gesture, Letts said.