HARRY Potter star Daniel Radcliffe's stage debut in the West End earned him a standing ovation, praise from the critics and a siege by fans that forced his co-stars to escape through a window.

The 17-year-old actor's performance - some of it naked - as a stablehand with an erotic fixation on horses - drew a star-studded audience to the official opening of Equus last night.

The Hollywood actor Christian Slater, the TV presenter Graham Norton, the singer Bob Geldof and his daughter Pixie all turned up - along with about 450 (mostly teenage girl) fans who gathered outside the Gielgud Theatre.

The crowd was so excited that Radcliffe's co-stars, Jenny Agutter and Richard Griffiths (Potter's burly uncle Vernon in the films), could not exit through the stage door.

"You try to get Richard Griffiths out of a back window. It was touch and go," producer David Pugh said.

Critics lauded Radcliffe's performance. "He has put Harry Potter tidily behind him - should he so desire," Quentin Letts wrote in the Daily Mail.

On the much-hyped sex scene with the pretty young actress Joanna Christie, he said: "There was no great moment of voyeuristic titillation.

"What was striking, instead, was the emergence of young Dan Radcliffe in the artistic raw, tested as an actor and found equal to a stretching role."

Thirty-something women who may have been salivating before "like Hogarthian trollops" were "surely left poleaxed by a great drama done well", Letts added.

The Guardian's critic Michael Billington gave Equus four stars. "Forget all the prurient press speculation about Harry Potter's private parts," he wrote.

"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."

Benedict Nightingale, in The Times, gave the play three stars. "Radcliffe proves an assured actor and makes a perfectly able equimaniac," he said.

"He can do aggression and pain, and, oddly, is lacking only in the sense of magic and wonder the part demands."

David Lister, in the Independent, said Radcliffe cut a "compelling figure" in the "best theatrical role for a male teenager".

Only Nicholas de Jongh from The Evening Standard were less impressed: "Radcliffe's touching, little-boy lost Alan never convinces you he is wild with desire for horses or girls. Equus still fascinates, but this revival lacks horse-power."

Christian Slater disagreed: "The work that Daniel did on stage was incredible, extraordinary. I take my hat off to him completely.

"He became Alan Strang. I never thought for one second I was looking at Daniel Radcliffe - I was watching Alan Strang."