IT’S the legs you notice first. On the poster for Dundee Rep’s forthcoming production of The Graduate, which opens this week, they pour seamlessly from the protective armour of a classic little black number into a provocative scissor-shaped stance. As images go, it’s an instantly familiar icon.

When Anne Bancroft’s Mrs Robinson attempted to seduce Dustin Hoffman’s nervy geek Benjamin Braddock in 1967, it wasn’t just Ben’s coming of age. Led blinking into the light by Simon & Garfunkel’s score, here was an America squaring up to a post-JFK, pre-summer of love aquarian age and a whole new set of values.

When Terry Johnson’s stage version of The Graduate took the west end by storm more than 30 years later, its appeal may have been born of nostalgia, but it was no less iconic. This was largely down to the casting of Kathleen Turner as Mrs Robinson. It may also have had something to do with a teasingly brief nude scene from the show’s leading lady.

A succession of Mrs Robinsons - Jerry Hall, Amanda Donohoe and Glynis Barber - did the rounds of chat shows, making slipping into Mrs Robinson’s negligee a scary prospect indeed for any actress. According to Dundee’s Mrs Robinson, Irene MacDougall, however, "all the furore over film stars taking their clothes off and who was going to do it next is something we’re benefiting from, because it means we’re already getting extra attention.

"That has a good side and a bad side, because people will come along expecting Anne Bancroft or Kathleen Turner, and they’re going to be disappointed because I’m neither of them, and I have to be careful as an actor that I don’t try to live up to that sense of expectation. There is an enormous sense of responsibility in these iconic roles". Indeed, it was the baggage of Mike Nichols’s big-screen version that almost dissuaded Terry Johnson from taking on what he admits was a commercially driven project. "I looked at the film and said no, because it was too iconographic. Then I looked at Charles Webb’s original novella, a wonderful piece of 1960s zeitgeist about American society, and realised the film owed far more to this work of literature than it’s given credit for. As I became convinced it could work, the play began to owe less and less to the film. All we stole from the movie is a couple of gags. The rest is four-fifths Charles Webb, one-fifth me." The Graduate’s instant success opened the door for a mini wave of films being put on stage, with the likes of The Producers and the just-opened Billy Elliot reversing a trend of stage adaptations making it on to celluloid. Johnson recalls how, six months into his play’s run, "one of the studios sent out a five-sheet document of film properties which they claimed were ripe for stage treatments".

Johnson admits, however, that, despite The Graduate’s UK success, "they didn’t really take to it in America, where there was a bit of a backlash. I think they felt we were just being uppity and English." One such sniffy American may well have been Marcy Khan, who adapted Nora Ephron’s equally iconic rom-com, When Harry Met Sally, for the stage. It, too, was a west end hit, and featured ex Brat-packer Molly Ringwald and Buffy The Vampire Slayer sidekick Alyson Hannigan faking the orgasm that made Meg Ryan famous. A touring version, starring TV presenter Gaby Roslin, arrives in Glasgow next month.

For Khan, the appeal of her adaptation lies in "seeing the familiar and the unfamiliar conjoined. When Luke Perry played Harry onstage, because he’s younger and more handsome than Billy Crystal is in the movie, he works even better as such a dude, and you realise more why he’s so successful with women".

For Khan, the traffic between film and theatre is a two-way affair, and nothing is sacred these days. She cites Play Without Words, Matthew Bourne’s contemporary dance version of The Servant, Joseph Losey’s class-centred film, which Harold Pinter adapted from a novel. "That is an imaginative take on its source, which is one of many ways you can go. You can be faithful to the original, go down an arty route like Matthew Bourne, or do what Billy Elliot and The Full Monty have just done and turn it into a big west end musical.

"The source of art," she says, "can come from any direction now, and these days books that aren’t even published yet are being hoovered up by film studios. The market is insatiable, and because there’s such a high volume of production, it’s inevitable that some good work is going to get thrown up. Just think of how many B movies were produced in the 1940s. No-one knew Casablanca was going to become the hit it became. It was just another studio movie."

Adaptations into myriad forms aren’t a new phenomena. Keith Waterhouse’s late 1950s novel, Billy Liar, was adapted for the stage before becoming a big-screen vehicle for Tom Courteney. In the 1970s Waterhouse and co-writer Willis Hall authored a TV sit-com of Billy, long before Michael Crawford starred in a smash hit musical version. Meanwhile, deep in the French nouvelle vague, Marguerite Duras’s texts blurred the lines between literature, drama and film script even further.

Johnson’s own play, Insignificance, was made into a film by Nicolas Roeg, and, given his work’s frequent imagining of real life figures, he admits to applying similar magpie techniques to The Graduate. "I’m more Rory Bremner than William Faulkner," he jokes. For Khan, in a parallel universe, When Harry Met Sally could easily have been a stage play on Broadway first, and only Nora Ephron’s immersion in the film world rather than theatre-land prevented it. "It’s a piece of classic rhetoric," she says of its wordy interplay. "It sets up a debate about men and women in the same way than an Aristophonic comedy does."

For MacDougall, When Harry Met Sally’s appeal is far simpler. "It’s a chick flick, but it’s a chick flick with a fake orgasm," is how she sees it.

Purists will always be disappointed when their memories of classic movies are seemingly desecrated by stage versions that, for them, can never do them justice. But, as Khan points out, "It’s like how people feel about Jane Austen. Some will prefer to read the book, while others can’t wait till the next adaptation comes along. What I would say to people who object to movies being adapted for the stage is, just relax. If it’s not any good, it’ll die out."

For The Graduate, at least, there doesn’t seem to be much danger of that. "It’s in the canon now," according to Johnson. "I think it’s going to go on and on."

Such confidence in his own material may sound self-aggrandising, but The Graduate is so much in the public domain that it’s just received its first request to be performed by an amateur company. "It’s from an Army base in Lincolnshire," Johnson deadpans. "What they’ll make of it, I do not know." Yes, but just imagine how well-drilled the legs will look on the poster.