"Demonic possession is not make-believe. It could become a frightening reality in your life today. Often it begins with curiosity and the desire to dabble, aroused by films like this."

So said Pastor Brian Grist from the Elim Pentecostal Church in St Peter's Broadstairs in a desperate bid to prevent the good folk of Thanet from venturing to the cinema in the summer of 1974 to view supernatural horror The Exorcist.

"What people do not realise," he added, "is that films of this nature can bring devastating results to peoples lives. It can shatter your emotions and could leave you in a permanent state of fear.

"A film like this draws evil forces which will surround the audience."

His comments made front page news of local newspapers at the time - and echoed those made nationally by many others.

Publicists today would pray for such a response; a knee-jerk reaction to hype (the pastor admitted he'd not actually seen the film) which has been proved, time and time again, to see controversy plus headlines equate to box office gold.

In other words, rather than persuading the public to turn their back on the movie, they flocked to it in their droves to find out what all the fuss was about.

This was, after all, in an era when cinema seats had to be secured by patient queuing, and word of mouth was the Twitter of its day.

In Tunbridge Wells, during the film's first week of release at what was then the Classic Cinema on Mount Pleasant Road, it reported 15 customers had fainted, prompting theatre bosses to ask teams from the St John Ambulance service to be on call at the venue to treat those for whom it was all a bit too much.

Back in Thanet, Margate's Dreamland's cinema screened the movie to packed houses. Local newspaper reports at the time talk of "hundreds of people" being turned away each night.

Canterbury City Council discussed calls for the film to be banned before saying the authority "weren't prudes" and permitting the film to be shown in the district.

But, 50 years from when filming of The Exorcist began, the reaction it generated paints a vivid picture of a very different era.

It's hard today to imagine a movie creating such a reaction. We have long been numbed to any number of horrific scenes created by special effects wizardry. Surely all so-called taboo topics have now been covered? The big screen has tackled almost all imaginable controversial scenarios - and, today, far worse can be found online.

Yet the foul-language, disturbing scenes and, at it's heart, the tale of a young girl possessed by a demon, seemed to be only the latest slipping of standards for Kent - and Britain as a whole - in the early 1970s.

"The Exorcist is a film whose reputation proceeds it - both then and today," explains Dr Frances Kamm, lecturer in film studies and director of education for film and media at the University of Kent.

"Speak to most people about what happened when it was released and they'll talk about people fainting, being sick or running from cinemas to churches.

"But put it into the context of the time and these conversations about what films were depicting were being had very publicly.

"That conversation was happening in the press and the reviews.Some critics were impressed by it, others who saw it as cynically exploitative.

"So by the time it was released over here, it was already framed with those controversies."

To set it in context, the US movie market was undergoing rather a dramatic shift.

In 1968, the so-called Hay's Code (or the Motion Picture Production Code to give it its full title) was brought to an end.

Named after William H Hays, a long-serving president of the Motion Picture Producers and Distributors of America (MPPDA), it was a self-imposed set of guidelines for the movie industry.

It prohibited profanity, graphic violence, suggestive nudity and had rules around religion and morality.

After gradually fading out, its departure at the end of the 1960s ushered in a new breed of film-makers - dubbed 'New Hollywood', keen to push boundaries.

Adds Dr Kamm: "Stephen Murphy, secretary of the BBFC (British Board of Film Censors at the time, the British Board of Film Certification today) at the time of the film's release said: 'It is my view this is a social phenomenon rather than strictly a matter of censorship'. So he was saying much of the fuss was largely imported and that there was nothing inherent in the film itself that was particularly alarming.

"Although that's not to say there aren't disturbing images in this film."

The BBFC ignored the calls for it to be banned and issued it an X certificate - preventing anyone under the age of 18 from viewing it.

Explained the BBFC: "It was perhaps unsurprising that the film's UK release provoked a certain degree of outrage, particularly amongst pressure groups. However, the film was a huge popular success at the box office and the public as a whole did not seem overly concerned.

Despite this, a handful of local authorities bowed to the demands of pressure groups and banned the film in their areas, which only added to the reputation of the film."

The Nationwide Festival of Light, a relatively short-lived, but high-profile, movement of Christians concerned about the social changes and permissive society ushered in during the 1960s, staged regular protests outside cinemas. It also piped up in a bid to persuade Sandwich council from allowing the film to be shown in the district. It failed.

The group, founded by the journalist and author Malcolm Muggeridge and TV standards campaigner Mary Whitehouse, did, however, succeed elsewhere.

Among those siding with the Festival of Light were a group of 'young Christians' from Whitstable who wrote to the local authority calling for it to be banned.

Their open letter said: "May we point out the possible dangers. The occult has nothing to offer the follower, but to the contrary, its effects can be disastrous. Physical dangers are great, especially following overpowerment by a possessing spirit, when the body is prostrated by the force overtaking the person. The mental dangers are tremendous."

It is, it must be said, hard to see how the film, directed by William Friedkin (who had already won as Oscar for French Connection in 1971), acts as any form of advocate for dabbling in the occult.

Given the vast number of films which have taken demonic possession as a central theme ever since, it's safe to report that the protestors failed miserably in their efforts and were no doubt horrified by the floodgates it opened.

As for the film itself? It has been hailed a classic of its genre and still holds power over audiences today.

Starring a young Linda Blair as the possessed 12-year-old and also featuring Max Von-Sydow as one of the two Catholic priests sent to carry out the exorcism, it was nominated for several Academy Awards, walking away with two. It was the first horror film ever to achieve a nomination.

Critically acclaimed, its reputation has grown over the years with its iconic - and often disturbing scenes - earning it a notoriety on which it continues to trade on today.

Adds the University of Kent's Dr Frances Kamm: "It still attracts attention for academic research.

"There's the gruesome depiction of a possessed child, but that also speaks to larger themes of abjection, female sexuality, blasphemy, the role of the Church, the role of the patriarchal family, all sorts of things which continue to inspire those sorts of debates and conversations.

"It was a really important turning point in cinema."

Meanwhile the film's reputation far exceeds the early 1970s in which is was released - helped by the belief that it was banned for many years in the UK.

It had, in reality, been available on home video for several years, but in 1988, after a change in video certification regulations, there were concerns it may be seen by those too young.

"It speaks to larger themes of abjection, female sexuality, blasphemy, the role of the Church, the role of the patriarchal family..."

Adds the BBFC: "Therefore, at the beginning of 1988, the video was removed from the shelves and was to remain unavailable for 11 years. Despite the prohibition on the video version, the film continued to play occasionally in cinemas, its existing X certificate being replaced by a new 18 certificate - for cinema release only - in 1991.

"In 1998, the distributors decided to celebrate the film's 25th anniversary by relaunching the film in UK cinemas. The re-release was notable in that it was not accompanied by any of the hysteria or audience disturbance which supposedly occurred in the mid-1970s.

"When the film was formally resubmitted for video/DVD release at the end of 1998, the BBFC concluded that The Exorcist, while still a powerful and compelling work, no longer had the same impact as it did 25 years before.

"Film technique and special effects had moved on a long way since then, and audiences - including, or especially, teenagers brought up on a range of modern multi-media output - were less likely to be affected. Correspondingly, the potential of The Exorcist to disturb a small, impressionable minority seemed to have been significantly diminished."