Harry Potter star Daniel Radcliffe received a standing ovation at the end of his West End stage debut in Equus.
Actor Christian Slater, Bob Geldof and TV presenter Graham Norton were among those who watched the 17-year-old actor at the Gielgud Theatre.
Radcliffe plays troubled stableboy Alan Strang, who has an erotic relationship with his horses.
Slater said: "The work that Daniel did on stage was incredible, extraordinary. I take my hat off to him completely."
He added: "He became Alan Strang. I never thought for one second I was looking at Daniel Radcliffe - I was watching Alan Strang.
"I'm remarkably impressed. I think he was brave, adventurous and courageous, he's a phenomenon and I would certainly love to work with him."
Newspaper reviews of the play have also been positive.
Michael Billington wrote in The Guardian: "The revelation of this revival is that Daniel Radcliffe really can act, proving that his screen appearances as JK Rowling's boy-hero are no flash in the magic pan."
A nude scene in the play has dominated headlines about the play since Radcliffe announced he was taking on the role.
But TV presenter Norton said: "Why do people keep asking about him being naked? I'm a gay man and I'm not mentioning it. It's a play - get over it, ladies."
After the performance, Radcliffe admitted the scene, with co-star Joanna Christie, was the talking point of the production.
"I sort of expected it really," he said.
"If I went into it thinking nobody was going to talk about it, I would have been very stupid.
"But it's not a big part of the play, it's four minutes at most."
Meanwhile Warner Bros, the studio behind the Harry Potter films, issued a statement denying reports it was unhappy with Radcliffe's appearance in the play.
The studio said it "fully supports him in the artistic choices he makes as an actor."