As Ozploitation films of the 1970s exploded with horror, action and violence, the movement also revelled in raunchiness. Relishing new-found artistic freedom, button-pushing directors soiled cinematic bed sheets time and time again during a sustained period of smuttiness unparalleled in Australian film history.

Movies such as The Naked Bunyip, The Adventures of Barry McKenzie, Number 96, The True Story of Eskimo Nell, Australia After Dark, Scobie Malone and Felicity presented all sorts of wobbly bits and sexual shenanigans. Average guy antihero Alvin Purple (Graeme Blundell) was at the heart of it, the floppy-haired centre round which all manner of carnal pleasures and perversities orbited.

Directed by Tim Burstall, the 1973 film that assumes his name was a big hit – so big it became the most successful Australian feature ever released at the time, chalking up over $4m at the local box office.

Burstall and writer Alan Hopgood exploited changes to Australian censorship laws made in 1971 by then federal minister for customs, Don Chipp, who introduced an R rating to reduce the number of films that were banned. This led to an influx of cheap imported sex movies and paved the way for Alvin Purple, a film with progressive instincts that were both informed and complicated by the emergence of feminism as a political movement.

It begins with Alvin sitting on a tram contemplating sexual temptation. “How can you keep your mind off it when it’s being flung at you every moment of the day,” he whinges via voiceover, observing an attractive woman with a T-shirt declaring: “Women should be obscene not heard.”

At home by himself, Alvin cracks open a beer and takes drastic measures; he declares celibacy and makes a toast to “the sexless 70s”. A moment later a pretty young neighbour appears at his front door asking for a cup of sugar. Thus begins a differently oriented decade: the sex-filled 70s, where Alvin can’t escape erotic encounters no matter how hard he tries.

In fact the harder he tries, the more situations he finds himself part of. The film’s central joke revolves around the idea that an everyday man, hardly a pin-up model, can be irresistible to women everywhere. More than that, Burstall reconfigures stereotypical gender roles, painting Alvin as a victim and women as sexual predators.

Sex is flung at him virtually every moment of the day, if not in actual encounters than through innuendo. “There are openings everywhere for the right man,” says Alvin’s father during his 21st birthday speech. “Find out what you want to do and then extend yourself.”

Burstall and Hopwood string together episodic situations such as Alvin escaping girls at school (he ends up sleeping with his teacher’s wife) and Alvin taking a job as a water mattress salesman (subsequent scenes practically write themselves).

After Alvin is recruited by a quack from a shonky psychiatrist’s office to be a kind of therapeutic sex worker, helping clients (mostly wives) conquer sexual fears and inhibitions, the practice is busted and the protagonist is put on trial to determine what – if anything – he is guilty of.

These courtroom scenes give Alvin Purple an intellectual anchor and solidify it as something more than a series of disconnected escapades. Alvin’s sort-of pimped services can be read as an equivalent for the movie, a bizarre anthem to giving the public what they want and rubbing it in the face of prudes who stand in the way.

“This trial has been one of the most enjoyable experiences in all of my 30 years on the bench,” the judge – having been treated to a range of racy films starring Alvin – declares prior to ruling. “Speaking as a judge, I found it a welcomed relief to the usual parade of wife beaters, drunks and tax evaders, whose antics I find of no entertainment value whatsoever.”

Those lines are key to the film’s legacy not as a raunchy comedy but as a spicy commentary on the censorship debate. Given the attitudes of today’s censors, who generally regard sexual representations with more suspicion and harsher classifications than violence, Alvin Purple won’t be going out of date any time soon.