It is 40 years since The Wicker Man was launched onto unsuspecting cinema audiences. Weird and unsettling, it was instantly hailed a triumph of British horror.

Since that time the movie industry has changed beyond recognition, with special effects allowing ever-increasing levels of terror and gore. Yet The Wicker Man remains a classic; a psychological thriller with a haunting folk soundtrack which, with its peculiarly British blend of paganism, sexuality and murder on a remote Scottish island, remains remains a cult favourite.

Just the perfect film then for a good old sing-along.

In a bizarre cross between the camp fancy dress silliness of the Rocky Horror Show and audience participation productions of such family-friendly films as Grease and The Sound of Music, musician and comedian David Bramwell and vocalist Eliza Skelton are leading a sing-along version of this most spooky of films. And a bizarre affair it is too.

Having already gone down a storm with audiences in their home town of Brighton, London, and, inevitably, Scotland’s Wicker Man Festival, they tomorrow bring the show to Oxford. Among the audience for the late screening at the Ultimate Picture Palace, in Jeune Street, off Cowley Road, will be the film’s director Robin Hardy, who will hoist a Q&A session with the audience — who are being encouraged to dress for the occasion.

“It’s a camp Rocky Horror-style cabaret and film night, combining live music, audience participation, sing-a-longs, bottom-slapping and other Wickerman-themed silliness,” says David.

Audiences are encouraged to come along dressed as their favourite character from the film (or, if they prefer, in nothing at all) and are provided with a “Pagan hymn book”, featuring the words to all the songs in the film and a goody bag full of mystery items to be used during the film.

“Ours is more low-fi than the usual sing-along productions,” says David. “There are no lyrics on screen or bouncing dots. We hand out Pagan hymn books and hold up cards — but we also warm the audience up before it starts. It’s more in the spirit of Vic and Bob than a West End musical.”

The film stars Edward Woodward as a devout Christian police officer who travels to an isolated isle to investigate the disappearance of a young girl. He finds a close-knit and secretive community, clinging to Pagan beliefs and ruled over by the sinister Lord Summerisle (a career-best performance by Christopher Lee). Among the islanders, who he comes to suspect of human sacrifice, is the beautiful Willow MacGregor played by Britt Ekland, whose attempt to seduce the puritanical police sergeant remains an iconic cinematic moment.

“It’s a dark, camp, psychological story of modern day paganism set on a Scottish island in the 1970s. It has hammy acting and great folk songs based on ancient lyrics, which catches the essence. But it is also about sexuality and freedom as they throw off the shackles of conformity and become heathen.”

Given the film’s quirky soundtrack, it is appropriate that the show is being presented by Oxford’s Irregular Folk promoter Verity Hoper.

It is not the first chance Oxfordshire movie fans have had a chance to join David and Eliza (who is the daughter of Roy Skelton, the original voice of the Daleks, and Zippy and George from Rainbow) in the sing-along thriller. The pair also staged the show at this summer’s Wilderness festival, near Charlbury. “It was great,” says David. “People came along to the festival with their costumes and stayed all the way through.”

So how did the idea come about? “Eliza and I play in bands and are also fans of music,” he says. “We thought it would be great to put on a night singing songs from the film and in a weird leap, came up with this.

“People often ask if there are songs in the film, but that’s one of the things that makes it so unique. It’s easy to forget how many songs are in it.”

And, he says, that is also what has helped it stand the test of time without looking dated. “Its lack of theatrical blood and gore, so beloved of the Hammer horror films, has kept it looking fresh. It is beautiful, naturalistic and enchanting with a strong story. I’ve seen it 70 times, or maybe more, and still love the music as much as I did when I first heard it.”

He adds: “It’s a big slice of fun. People come in the most amazing costumes, and we have prizes for the best. One man came dressed as a wicker man made of bamboo blinds, but we get lots of people in white robes, tweeds and fisherman’s jumpers — and the occasional policeman.

“The only thing that is dubious is that we are unashamedly getting the audience to collude with the islanders — and, if you know what happens at the end of the film, you’ll know