When Richard OBriens musical The Rocky Horror Show was first staged late at night, at the small Theatre Upstairs at the Royal Court in 1973, it rapidly became a cult phenomenon.

The B-movie-inspired story of the naive Brad and Janet entering into a world of transvestites, aliens and fishnet stockings went on to become a Broadway production.

Then in 1975, the film adaptation The Rocky Horror Picture Show came out, which according to reports, has the longest theatrical release in cinematic history, and can still be seen on the big screen today.

With fans crying out for more, OBrien then penned a sequel Shock Treatment, which was released as a film in 1981 and featured many of the same actors and songs of a similar ilk.

However, the film which follows Brad and Janet into a town that doubles as a TV station, failed to get a theatrical release and remains little known even to some Rocky Horror fans.

Now, 34 years later, Shock Treatment is going back to Rocky Horrors roots and is being staged as a play for the very first time at the Kings Head Theatre in London with the blessing of writer Richard OBrien and music composer Richard Hartley.

Hartley, who turned out for the shows dress rehearsal, said: The film was a bit of a mess really but we always thought we had some good songs and when Benji approached us about putting it on stage, I thought why not? Its been completely reimagined by Tom Crowley and its become a show for today.

Benji Sperring, the director of the show, said: I think the biggest shock is in the original movie there isnt any shock treatment. They dont really explore that so weve put it in, he said, adding: Its going to be really different. If they know the original film, theyll see where it comes from and theyll see what the starting block is but the path that weve taken to adapt it for the stage is really different.

Sperring pursued OBrien for nearly 10 years to get the rights to stage the show, and finally the actor and writer relented but with one specific instruction – to have the production put on in a small venue like Rocky Horror.

When I was talking to Richard Hartley and Richard OBrien, they wanted something which was up close, that there was no escaping, so we really focused on that, alongside making sure that we were able to explore all of the avenues that were needed, that we could go through the audience, that we could go into the audience, that we could engage with the audience and bring them up on to stage, said Sperring.

Both the play and the film of Rocky Horror have become interactive experiences, with audiences dressing up and interacting with the characters on screen or on stage. Sperring has taken into account that the same thing could happen with Shock Treatment.

Weve got no idea if the audience will get up and get involved or if theyre going to sit back and be passive or if its going to be a very active piece. We dont know which way its going to go, said Sperring. The actors are prepped as much as they can be and theyre aware that theyre just having fun. Richard OBrien said very early on: Let fun be your guide and as long as youre having fun, the show will be all right.

The show features West End performer Julie Atherton as Janet, and ex-soap star Mark Little as Farley Flavors, the media magnate who owns the TV-show town Denton.

Shock Treatment is running until 6 June at the Kings Head Theatre in Islington, London.