Rocketman actor Taron Egerton collapsed on stage during the opening night of his new theatre show.
The star was forced to leave the stage at the Ambassadors Theatre in Leicester Square after he passed out.
Egerton's understudying Joel Harper-Jackson then stepped in to play the park for the rest of the performance.
The 32-year-old reassured his fans that he was feeling much better and would be returning to the stage on Monday.
He said: "I am completely fine. Slightly sore neck and a bruised ego, but I'm fine."
He said he would return to the stage on Monday night.
"As some of you may have heard, I passed out during the first performance of COCK last night," Taron wrote on Instagram.
"I've decided to put a positive spin on it and I would appreciate it if anyone who was in the theatre last night just said that I gave such a committed, electrifying performance that my body couldn't handle it and check out.
"That being said, apparently you're meant to actually do the full show and not just three quarters of it. So I'll be back with a vengeance tomorrow night.
"That you to the amazing team at the theatre and my wonderful cast mates for being so lovely.
"But mainly I wanted to say thanks to Joel Harper Jackson who stepped in to do the last bit of the play.
"Joel is an amazing actor and a lovely person. Thank you, Joel. T x."
A statement from the play's production released last night said: "During this evening's first preview of Mike Bartlett's play Cock at the Ambassadors Theatre, Taron Egerton fainted towards the end of the performance.
"A doctor who was in the audience attended to Taron immediately after the incident, and whilst he felt fine, it was decided that Taron's understudy, Joel Harper-Jackson would continue in the role to complete the performance."
