`I never thought of The Exorcist as a horror film," says William Friedkin. "I never set out to make it as a horror film. I realised it would have quite intense subject matter and I tried to present it as realistically as possible in a way that would make the audience suspend disbelief. I approached this as a realistic film about inexplicable things and therefore I wanted the audience to believe what they were seeing. I didn't want to push the envelope too far."
He cites the scene of the possessed child coming downstairs, backwards and upside down like a crab which he cut because, he says, he felt it was over the top. And he has resisted all efforts since to reinstate it.
Friedkin's emphasis on realism can be traced back to his beginnings as a documentary film-maker. From the outset he showed a maverick streak, difficult or contentious subject matter was grist to his creative mill. The People v Paul Krump set on Chicago's death row, made when he was only 24, was so harrowing it was banned by the TV station that commissioned it, but went on to win the Golden Gate Award at the 1962 San Francisco Film Festival.
Friedkin's documentary fingerprints are clearly visible on The French Connection, which won him an Oscar in 1971. He wrote the script himself, spending two months working and travelling with the real New York cop the story was based on.
The reality factor also affects his casting decisions. "I always try to cast people, if I can, as close to what they already are and understand," he says. In The Exorcist Max Von Sydow was cast because he looked like Teilhard de Chardin, the theologian on whom Von Sydow's character of Dr Merrin was based. For the girl, he refused the studio's suggestions of 17- or 18-year-olds. No matter how young they looked, he believed, they would not have the innocence the part needed. Linda Blair ("A gift of the movie god") was 12.
When it came to the guilt-ridden young priest Father Karras, he turned down both Jack Nicholson and Paul Newman. "I didn't want to see a major star wearing a dog collar, especially an actor who had a personal life that was public enough to clash with that image." Instead he cast a Jason Miller, a playwright.
"He had written a play called The Championship Season, that went on to win a Pulitzer Prize. And I saw something on the stage that had a lot of the qualities that I was looking for in The Exorcist. The characters had a lapsed Catholicism and a brooding self-denigrating nature and each in his own way was going through a crisis of faith." It turned out Miller had even trained for the priesthood.
The realism of the exorcism ritual enacted in The Exorcist was an important part of the marketing strategy, and the overt support of the Catholic Church was sought, found and, dare one say, milked. Friedkin himself is Jewish. But he had no problems with the premise of the film. He was given access to the archive material - diaries and medical records - relating to the 1949 incident by church authorities. He filmed in a Jesuit residence in Washington. Another priest in the cast, Father Dyer, was played by the real Jesuit, William O'Malley.
Priests were also on hand when Mercedes McCambridge recorded the sound track to represent the demon inside the possessed child.
"The demon voice had to sound neutral," explains Friedkin, "neither male nor female and coming from another place. So we did certain things in order to achieve this. We would give her a drink made up of raw eggs and whisky and she'd smoke two or three packs of cigarettes and by 10 or 12 o'clock in the morning various wheezes would develop in her throat. She knew how the alcohol would affect her voice, and she knew if she could use it to provoke this sound in her throat that it would be good, and it was." She knew, because she was an ex-alcoholic who had also given up smoking. Hence the bizarre presence of the two priests to help her through the ordeal.
To make the moans and screams as realistic as possible the veteran radio actress was tied to a chair. "It made it easier for her," explains Friedkin.
"She wanted to feel pain. She knew she could convey the sound of pain better if she felt the pain. I didn't participate reluctantly, but most of these things were her idea."
With his slicked back hair, steel-rimmed glasses and co-ordinating olive green shirt, trousers and tie, William Friedkin looks like an army officer. And like an army officer, control sometimes breaks into spleen. When I ask what he thought of Exorcist II the Heretic, he nearly explodes. ". . . travesty . . . one of the. worst films every made . . . Richard Burton ludicrous . . . unspeakable . . . people would run out and demand their money back in droves . . ."
When I ask why he thinks his own career has never returned to the Oscar heights of The French Connection and The Exorcist (nominated for seven, won two), he says he doesn't know. "I think any success is by the grace of God. Paintings by Vincent Van Gogh never sold in his lifetime. They were literally worthless. And Van Gogh died very down-hearted at the age of 37. Now he's recognised as the most talented, the most in-demand artist that there is."