The Kinsey report

A biopic of Alfred C Kinsey, starring Liam Neeson, has proved as controversial as his notorious surveys on sexual behaviour. Jonathan Gathorne-Hardy, his biographer, goes on set

The film was being shot at Letchworth an hour from New York, over the Hudson, and then north through rolling woodland. The actors involved that day and the technicians had already been at work for two hours when my car, supplied by Fox Searchlight, arrived in front of a long, low building.

I was led upstairs, stepping over cables, slightly nervous at trying to enter that bubble that forms around groups engaged in intense endeavour - actors, footballers, platoons in battle. Bill Condon, the director and scriptwriter (as he was of Gods and Monsters) came out of a crowd at the end of a long, cluttered room. To one side, apart, abstracted, I had already noticed Liam Neeson, his head down, reading his Kinsey script, chewing on a toothpick.

Bill said: "Good to see you again. Come and meet Liam." The actor came over. He looked tired. I said he reminded me strongly of Alfred Kinsey. He even stooped like Kinsey, who had rickets as a child. Neeson said how much he'd enjoyed my book. (My passport into the bubble was my biography of Kinsey, which Bill and I had met to discuss four years previously.) "You've even got his stomach," I said. "Yes - false, I'm glad to say." I remembered how Kinsey, too, had always looked tired.

Although they had been shooting Kinsey for seven weeks, and there remained only four days, they were, by chance, about to do the short opening sequence. Neeson and Peter Sarsgaard, who plays Clyde Martin, one of Kinsey's young, good-looking assistants, go into a cubicle constructed at the end of the long room. Six or seven figures follow them, including Bill Condon. I am given earphones attached to a receiver and invited to sit in front of the little monitor. My canvas chair has "Clara Kinsey" written on it in large letters. We wait. Nothing happens.

Shooting a film is like being in a battle: minutes, hours even, sitting about. Suddenly, a burst of activity. I can see Neeson on the little screen, chewing his toothpick, his mouth moving, sinking deeper into Kinsey, oblivious that someone is brushing his hair, dusting his forehead. Light screens are moved, sound levels tested, light levels tested, more light screens. Neeson sips from a Thermos...

At last, Bill darts out, puts on earphones, and sits in front of the monitor. One of the young men, in loose, baggy shorts, floppy pockets bulging with pincers, camera, cellphone, shouts: "Quiet! Shooting!" It is taken up by a young woman at the far end of the long room, and echoed again, distantly, down the stairs. Bill Condon calls out, "Action", and I switch on my receiver.

Kinsey: "Don't sit so far away. Anything that creates a distance should be avoided. And try not to frown."

Martin: "I'm sorry. Was I frowning?"

Kinsey: "You have to relax. How can I be expected to open up if you're not relaxed?"

When, after 20 years as an entomology Professor at Indiana University, and appalled at the guilts and anxieties that ignorance about sex caused his students, Kinsey decided to take up sex research, he realised that the most difficult thing would be to get people to tell everything, and to tell the truth. He devised his own interview technique, a technological tour de force that has never been equalled. Martin is learning how to interview.

Martin: "As you can see, this piece of paper has been divided into 287 squares. Your sex history will fit on to this single page."

Kinsey: "Don't forget to mention that there's no written key to the code. The interview subject will only be candid if he knows he's speaking in the strictest confidence."

At the fourth take, I suddenly realised why Neeson reminded me so strongly of Kinsey, and why he was an inspired choice. It wasn't in fact his appearance, despite the stomach. Kinsey had a thicker face, with jowls, where Neeson has leanness (though Neeson has the same severe, rather gloomy expression). It is a certain power, something that makes itself felt in his major films, even his recent K-19: The Widowmaker. There is an electrifying moment at the end when Neeson, as Mikhail Polenin, suddenly seizes the film and for five minutes dominates it completely.

"You felt," the American writer John Tebbel said about meeting Kinsey, "you could actually feel that here was someone outstanding. He emanated power. The only other person I met, who seemed at first mild, but radiated power and strength in the same way, was Einstein." Even with my crackling earphones and the tiny screen, it was a power that I could feel coming through the monitor.

At last, after nine takes and three hours work, five minutes of film were completed. Walking back to lunch was like walking back through Kinsey's life. I recognised a block of false brickwork from the house in Bloomington where Kinsey and Mac, his wife, had lived; further on, pushed back, some items selected from Kinsey's vast collection of erotica - 17th-century dildos; a 3in miniature of an innocent-looking cupid fellating the extremely large penis of another smiling cupid; decorative condoms. At the top of the stairs, a vast array of gall-wasp boxes, the subject of his entomology. Going downstairs, I passed a technician in the obligatory loose, baggy shorts, chewing on a toothpick, and a moment later, another doing the same. Neeson had started a fashion.

Film crews seem to eat well. I sat at a table with Bill Condon and Gail Mutrux, the film's diminutive, attractive, determined producer. In the 45 years since Kinsey died, there had been numerous attempts to mount a biopic. Only Gail had succeeded. It was reading my biography, I was pleased to learn, that had made it seem possible. She had shown the book to Bill. It had taken them both five years to get a film off the ground. I asked when it would come out. Gail said that if they felt it was good enough for the Oscars and other prizes, autumn 2004. Otherwise, spring.

After lunch, I walked round the Letchworth lot. Again, I was reminded of an army on manoeuvres, but a driver told me that this was nothing - 75-100 people a day. He had worked on Terminator 3 - "That was 500-600 people a day, or more."

I talked to Richard Sherman, the production designer. "It was difficult. They don't make period films in New York. Kinsey goes from 1894 to 1956. Huge changes. Take college desks in 1930. In LA, I could hire 25 for $6 a day. Here, I had to make them - $6,000."

He had had to build the Bloomington house, a chunk of which I'd seen back on the set. He said that he'd had an eerie time getting the wallpaper. He'd gone to a shop specialising in replicas of old papers. Chose one. Turned it over, and on the back was printed the name Kinsey's Garden... "I can tell you, goose flesh went up my back." The shopkeeper was vague - it was some doctor famous for his garden. I told Sherman that this was correct. In the Twenties and Thirties, Kinsey was a fanatical gardener. Obsessive in whatever he collected - gall wasps, erotica, sex statistics - he grew 250 irises. People came from miles to see them.

I watched further hours of shooting for a few more minutes of film, then, wishing I had a 10th of Liam Neeson's stamina, was driven back to my hotel. I reached it, overwhelmed by jet lag, at 8 o'clock.

The shoot the next day was at Lake Wawayanda, set in a forest. This was what you might call the masturbating sequence, important both for showing what Kinsey had gone through as a boy, and why his research was so necessary. At 19, Kinsey was an enthusiastic and handsome Eagle Scout. Now (played by Benjamin Walker) he is beside the lake, with a younger, equally handsome scout, Kenneth Hand (Mike Thurstile). Hand has just confessed that he has had "one of the old fits again". Young Kinsey pulls out the scouting manual and reads (an actual quote): "Doctors link it to an assortment off illnesses, including insanity, blindness, epilepsy, vertigo, and even death."

Hand: "What if it happens while you're asleep?"

Young Kinsey: "It says that the loss of 1oz of seminal fluid equals the loss of 50oz of blood."

Hand: "I'm killing myself and I'm not even awake."

In the end, the two boys decide to pray. It was a scene that Kinsey himself used to recount. It was short, but it was bedevilled by a technical difficulty - Young Kinsey's nose. It had been given a latex extension and, in the hot sun, kept on melting. He had to keep on leaving the rock to have it reset. Eventually, someone held an umbrella over it and the nose held.

The previous scene, in fact shot next, also had difficulties. Here, Hand is looking at a jay in a tree, while Kinsey, gazing at him, says: "That's a mating call." The difficulty here was the bird. A short, thick-set man would gingerly climb into the tree, then shrink back for the scene to be shot. At once, the bird turned and dived into the lake and the man had to hurry down and rescue it. Time after time, he climbed up; time after time the suicidal bird dived into the lake. At last, he went and got another bird that sensibly sat tight.

Intrigued, I caught up with Steve of Animal Actors Inc. Yes, it had been tricky. He knew he was in for trouble when the bird kept looking at the water. They were Java doves, not jays. He also trained elephants, cows, dogs, cats... any animal you mentioned, Steve had trained it. He said that he and his wife came to Yorkshire each year to walk. She was William Hague's sister. "You mean the last Conservative leader?" "Yes." "I bet he's a good deal happier now." "Darn right he is."

Lunch was in a big open-sided tent in a clearing. I sat with Bill and Gail again. I knew this series of scenes ended with Kinsey alone in his tent at night. He masturbates. Then, overcome with fear, guilt and remorse, bursts into tears. I was interested to see how this would go. "I'm afraid it will be a closed session," said Bill. The scene in which Clyde Martin seduces Kinsey had been closed; also one of Liam in bed with Laura Linney, who plays his wife, Mac.

In fact, Liam introduced me to Linney later that day, back on the set at Letchworth. She had just been starring alongside him in Love Actually, the Richard Curtis film. I liked her at once. She was quick, humorous, lively, intelligent; she was not, however, plain. I knew efforts had been made to bring her closer to Mac in this respect. She said that they'd hidden her long hair under a wig. Also, "My eyes are blue, not brown," and, disconcertingly, she slid a brown pupil to one side and revealed a cornflower-blue one underneath.

But it was while talking to her, and Timothy Hutton, who plays Paul Gebhard, the last of Kinsey's three assistants, that something I'd been aware of but had not formulated was suddenly made clear. The storm of fury and vilification that greeted Kinsey's Female Report in 1953 led to the abrupt withdrawal of his funding; it was this, along with years of chronic overwork, that destroyed him. The reaction was so vitriolic because the religious right, the conservative Republican right, was in the ascendant, their paranoia (and power) fuelled by the Cold War. But as a result, and ever since, Kinsey has been seen as a symbol of liberal tolerance.

Now, the right is in the ascendant again. And they are, said Laura Linney, still trying to dictate how people behave in their personal lives: condemning homosexuality and abortion; trying to ban sex education; disapproving of sex outside marriage or before it, and much else. They accuse Kinsey of paedophilia and of falsifying his homosexual figures; both untrue, both easily refutable - but the right wing are not interested in the truth. Last year, they made furious efforts to stop the film from being made.

Liberals are angry and frustrated, about these things and others. The element of crusade that drove Kinsey and his team, to an extent drives this film, too, which is why all the actors agreed to smaller fees.

It is a moving film and a brave one. Bill Condon doesn't evade any side of Alfred C Kinsey - not his bisexuality, for instance, or the way he encouraged very free behaviour among his associates. It is certain to arouse fury on the right, just as its subject did.

Jonathan Gathorne-Hardy's biography, entitled 'Sex - the Measure of All Things - A Life of Alfred C Kinsey', is to be republished to coincide with the release of 'Kinsey', the film