Even in Soho the sight of Richard Griffiths, one of Britain’s most illustrious and generously proportioned actors, escaping a mob through a theatre window is unusual. When the theatre involved is hosting the nude stage debut of a teenager better-known as the screen Harry Potter such pandemonium is probably inevitable.

Tonight is the opening night for the first major revival of Peter Shaffer’s Equus since its premiere at the National Theatre in 1973.

All the advance attention has centred on the casting of the 17-year-old Daniel Radcliffe as the lonely teenage stablehand who not only blinds several horses but also swears, smokes and strips off for a ten-minute sex scene with his co-star Joanna Christie.

Radcliffe has been playing the schoolboy wizard since he was 12 and will appear in the fifth instalment in the Potter series, out later this year. According to the Sunday Times Rich List, he is the country’s wealthiest teenager, with an estimated fortune of £14 million.

At each of last week’s preview performances, hundreds of fans gathered at the stage door after the show, hoping to persuade Radcliffe to sign Equusprogrammes and posters. Those brandishing Harry Potter memorabilia are moved on.

The frenzy reached a peak on Saturday night when a crowd of 450 had to be dispersed by police. The Gielgud Theatre’s security staff managed to escort Radcliffe to his car but two of his co-stars, Jenny Agutter and Griffiths, were trapped inside.

David Pugh, the play’s producer said: “Richard and Jenny had to get out through the side window by the box office on Rupert Street.”

For Griffiths, the award-winning star of Alan Bennett’s The History Boys, this proved a particularly delicate task. “You try to get Richard Griffiths out of a back window,” Mr Pugh said. “It was a bit touch and go.”

At least the actor would have had an idea what to expect when he agreed to play Martin Dysart, the psychiatrist who attempts to unravel the forces motivating Radcliffe’s Alan Strang. The “Pottermaniacs” flocking to see their favourite schoolboy wizard on stage would also recognise Griffiths as Uncle Vernon from the Harry Potter films.

The original production of Equus starred Peter Firth as Strang and Alec McCowen as Dysart. The play transferred to Broadway, with Anthony Hopkins as Dysart, and in 1977 was made into a film starring Richard Burton.

Shaffer, 80, had hitherto refused to sanction a major revival, partly because he did not previously believe that another young actor could match Firth’s performance.

Mr Pugh estimates that half the audience in the previews was made up of “people that don’t go to the theatre”.

“It was only after Peter Shaffer approved Daniel’s casting that we thought, ‘Ooh, what about the Harry Potter fans?’.

“We were incredibly nervous about security and we consulted the Rolling Stones security team. They told us to chill out.

“My main concern was that the sort of audience we would be getting might be a touch rock’n’roll, a touch Take That — the sort of people who didn’t understand theatre etiquette.

“But, touch wood, there has not been a single giggle or whoop or cheer.” During the nude scene, Mr Pugh said, “you could hear a pin drop.

“It’s been better than some of my nights at the National and if these people come back to the theatre that would be a hell of an achievement.”

The number of cameras confiscated on the way into the theatre each night and the online trade in Equus memorabilia and photographs suggest that for many Harry Potter fans the experience remains much more about Radcliffe than about the theatre.

Hollywood stars have become a fixture in the West End but few can have created as much of a stir as Radcliffe.

“People can get rather overexcited when big-name stars strut their stuff on the West End stage,” Alistair Smith, the news editor of The Stage said, but there had been nothing like the hysteria over Radcliffe’s appearance in Equus“since Nicole Kidman appeared nude in The Blue Room. Whatever the reviews say, his presence has made the production all but critic-proof as a commercial venture.”

What they said

“ I’m gay and as the theatre is on the edge of Soho it’s in just the right area. Lots of my friends are going to come to see it. I saw the pictures in magazines and he doesn’t look too bad naked” Chris Theobald, 22, a chef

“I’m excited about seeing him naked. I’m not a regular theatregoer. My sister didn’t want me to come because he takes his clothes off. I’m in row E but I wanted to get closer to the stage.” Aline Schuh, 16, an A-level student

“I saw Harry Potter and I loved it and I love Daniel Radcliffe too. In Georgia you don’t get famous people taking their clothes off in theatres so this will be a first for me.” Natia Gotua, 22, from Georgia

“Daniel Radcliffe just made us come. I heard it was a good play but I like him too. I feel like I’ve watched him grow up through the Harry Potter films. My hands are going to be in front of my eyes when he gets naked” Laurie Bulala, 38, a nurse from San Diego

“I’m a big Harry Potter fan but I’d prefer it if he wasn’t naked. I think of him as little Harry Potter” Aimee Elder, 24, from Atlanta

“I think I can draw the line between Daniel Radcliffe as Harry Potter and naked onstage but when I see the next Potter film I may have a different perception” Sara Kimberley, 25

“It’s a damn good play by a damn good playwright and it’s been my favourite play since I was a child. If anything, Daniel Radcliffe puts me off” Simon Wood, 42, from Reading

All those quoted were waiting to see last night’s production

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