AROUND 500 people attended the opening night of The Rocky Horror Show at the Royal Court Theatre in London in 1973. Mostly, they liked it. The reviews were good. Jack Tinker and Michael Billington couldn't say enough sweet things about it. The show was, by any measure, a success. But nobody who saw it then could have begun to predict the repercussions of what they had just seen.

Who could have predicted that the show would run until the 1980s? Who could have known that a movie version of the stage show would have, by the 1990s, earned its producers $180 million from their $1.25 million investment? Who could have begun to dream that there would be thriving fan clubs around the world? Who could possibly imagine that the project would, years later, spawn people like Sal Piro, president of the American fan club, who currently holds the record for "seeing the story told most often" (nearly 1,000 times, in fact).

Last summer Michael Scott directed a new Dublin production of the show, which is now about to take up what may eventually be a long residence at the Olympia Theatre - although, for the moment, a mere 14 performances have been scheduled.

Scott first tried to direct a version of the musical after seeing it in London, at its Kings Road home, in the 1970s. The first production of the play moved from the Royal Court to a venue which, in retrospect, seems far more appropriate: Chelsea's then crumbling Classic Cinema, before moving to the West End, where it closed in the autumn of 1980.

The musical was written by an Englishman, Richard O'Brien, who had spent most of his early years in New Zealand before returning to London. Early work as a film stuntman encouraged O'Brien to consider a career as an actor but his songwriting soon led him in another direction. O'Brien had already appeared in such typical movies of the day, as Hair and Jesus Christ Superstar, when the idea came to create a theatrical setting for several songs he had already written.

"I had just been let walk from Jesus Christ Superstar, basically because I wasn't really right for the part. It wasn't really because of anything I was doing wrong but one way or another, it did nothing for my self esteem," says O'Brien. "I was sitting, feeling rather depressed, in a lone room flat with a friend, explaining how I didn't really want to do Jesus Christ Superstar anyway, because it wasn't the sort of musical I liked. The sort of thing I wanted to do would be much more like a kind of rock n roll, horror, B movie musical. So we decided to write one."

One key ingredient is missing from O'Brien's description of The Rocky Horror Show - sex. When Brad and Janet find themselves stranded in a remote spot, they are delighted to spot even a spooky old house in which they can seek help. Inside, however, they receive a welcome more warm and intimate than they expect, when the master of the mansion, one Frank N Furter, a friendly chap in make up, stockings and suspenders, decides to turn these nerdy straights on to the swinger's lifestyle and give them ample opportunity to explore the limits of polymorphous sexuality which was probably in evidence at quite a few parties in the warm evenings of 1973.

"They weren't just exploring transvestism, homosexual sex, lesbian sex, incestuous sex," says Michael Scott over a sugar dusted white chocolate muffin and a cappuccino. "All were in the same show and they were all being put on the English stage just when the Lord Chamberlin was saying - `Now how can I close that down? My powers are going'. It was a very provoking thing happening."

Transvestism in itself would not necessarily have been a very provocative motif being a sturdy theatrical tradition, running at least from Elizabethan drama up to Peter Brook's Theatre of Cruelty.

This latter was a development, Scott points out, which was contemporaneous with The Rocky Horror Show. It took something of a novel approach to the subject, however.

"When you look at work like Genet's The Maids, which was taken by Brook, with all that work on Artaud, into the English speaking theatre, you can see this European idea of this supposed perversion where we're almost supposed to look at them and say `Aren't they sick people?'. Whereas with Rocky Horror, again you have the idea of men in tights, but you have people saying `I like this; this is me'."

"I like this; this is me," is obviously something that occurs to many people when watching The Rocky Horror Show. Despite any merits in Richard O'Brien's songwriting, storytelling and social criticism, what has really set the show apart from any other musical is the response of its audiences.

Whether you are a true believer or not, Rocky fanaticism is clearly more of a religion than a hobby. When Scott's production of The Rocky Horror Show first opened at the Tivoli this summer, it was clear that the word had gone out to the Rocky community. In pubs in the Thomas Street area, drag queens of all shapes and sizes could be seen trying not to look nervous, while inside the theatre, Aidan Conway as Frank N Furter had a running battle to keep ahead of the ranks of men in stockings and suspenders jockeying for position and calling out his lines.

Far more than any crusty, Anglo French, theatro circus company touring experimental revivals of Greek classics ever could, The Rocky Horror Show embodies the spirit of the carnival. The show may have started as a glam rock musical but it has become something much more.

During a performance, or a screening, the distinction between what the actors are doing and what the audience is up to fades. The script is malleable, regularly re written along democratic principles. Most of all, performances can only happen when a roomful of errant voices - scripted, unscripted, veteran, neophyte, gay, straight, bi, confused - combine in an eager polyphony.

So, is Richard O'Brien an aficionado of the writing of Mikhafl Bakhtin on carnival (a text which first appeared in translation around the time O'Brien appeared in the West End)? "Sounds like we're talking about someone middle European. I don't know him but I think he wasn't alone in those ideas. Joan Littlewood was doing very much the same thing. She used to say `the theatre is not a church' and that's definitely was been part of my driving force. I've always though you have to walk over the footlights".

O'Brien, who directed a version of Genet's The Maids while at drama school in the 1960s, is clear about how he sees his greatest work fitting into the traditions of experimental theatre. "I was very aware of Genet and The Living Theatre and all that explosion that happened in the 1960s. It was fascinating and very useful. It was new blood, like finding a fresh gene pool... a breath of fresh air blew into the theatre in the 1960s and, indeed, I did see the Rocky Horror as a part of all that."

Whether or not fans have delved much into the forces in experimental theatre which brought Rocky into being, O'Brien has undeniably given life to a strange, seemingly unstoppable creature - a cult whose followers maintain an unfathomable devotion to this particular rock show, a cult which exerts a total grip on the lives of those who fall under its spell.