HANNIBAL Lecter, the world's most famous cannibal killer, is about to horrify movie-goers as he slices, dices and munches a feast of human flesh.

Returning to UK cinema screens, in the sequel to Silence Of The Lambs, Hannibal once again terrifies audiences with his menacing grin and cold, steely gaze.

But at least there is the comfort of knowing that the serial killer with a taste for human liver and brains, is just fiction. Or is he?

Roaming the streets of Japan right now, free to go where he chooses, is a real-life Hannibal called Issei Sagawa.

One afternoon in Paris in 1981, Sagawa invited a girl he had befriended back to his flat, shot her and began to devour her body.

While all other known cannibal killers are either in jail or dead, Sagawa has been released by the Japanese authorities and lives unsupervised in a small flat just outside Tokyo.

Sagawa, now 51, admits he was obsessed with cannibalism from the age of three when his uncle used to play a game pretending to be a flesh-eating giant. He says that killing and eating his friend, Renee Hartevelt, was the fulfilment of a lifelong desire.

Sagawa recounts the gruesome incident to a Channel 4 documentary team and describes how he cut it up with a knife and fork before eating the flesh.

Sagawa was interviewed for the documentary in the middle of a busy shopping centre in Tokyo. Leaning casually against a railing, the killer, who is tiny and wears yellow-tinted glasses, speaks with eerie matter-of-factness.

He obviously liked it, for Sagawa kept a store in his fridge. He eventually tried to drag two large suitcases, filled with body parts, through the streets - with the aim of dumping them in a lake.

When spectators stared, he took fright and abandoned his load. It didn't take the police long to discover the contents of the cases and to track him down.

Sagawa is free today because a French judge decided in 1983 that he was mentally incompetent to stand trial and should be placed in a secure mental hospital indefinitely.

Less than two years later, he was sent back to Japan, where the police wanted to reopen the case and try him for murder. But the French refused to hand over the dossier and, in 1985, a hospital superintendent decided he'd had enough of holding him and simply set him free.

Today, Sagawa says he will never kill again. But neurologist Professor Jonathan Pincus, who has read his psychiatric report, was horrified to learn he was loose - and doubts whether Sagawa can keep his word.

The Channel 4 team also visited another real-life cannibal, an American named Arthur Shawcross, in his New York State jail.

Shawcross committed 11 murders between February 1988 and January 1990. Nine of his victims were prostitutes and he boasts that he ate some of their sexual organs.

Shawcross, 55, is fat, wears glasses and sports a tiny ponytail. He is separated from his interviewer only by a tiny wooden table. There are no screens or metal grilles. He claims he first tried cannibalism in Vietnam - and describes killing, cooking and eating a woman in front of her friend in the jungle. There is a twinkle in his eye as he recounts this tale.

Both Shawcross and Sagawa are clearly deranged. And yet, Daniel Korn - series producer of the Cannibal programme, and one of three authors of a new book, also called Cannibal - says they don't fit our stereotype.

Korn says: "I think what is most disturbing about these people is their banality, their normalness. It is not as if they are a spectre of evil because that is probably what you are expecting.

"It's the fact that these are everyday people, yet they are capable of these acts of unimaginable savagery."

Even more alarmingly, Korn and his fellow authors believe cannibalism is not restricted to the criminally insane - in fact, it has always been a central part of human behaviour.

He says, 800,000-year-old bones bearing signs of defleshing or "the cannibalism signature" have been found at Gran Dolina in Spain.

Bones dating from 12,000 years ago, with similar marks, have been found at Cheddar Gorge in Somerset - and more, from around 3,000 years ago, were unearthed near Eton College.

In the Aztecs or Old Fiji, man-eating was practised on a large scale as part of spectacular rituals. Other cultures, like the ancient Yanomami Indians of Central Amazonia, ate their dead out of love as part of the mourning ceremony.

And in times of starvation, when the choice was to eat one another or die, man has seemingly turned to cannibalism quite easily. The survivors of the 1972 Andes aircrash did it - as did marooned sailors in days of old.

Korn believes that, beneath the veneer of civilisation, cannibalism is "a very natural, latent characteristic of our behaviour". In other words, the cannibal is buried deep within us all.

l Hannibal opened at UK cinemas yesterday. Cannibal by Daniel Korn, Mark Radice and Charlie Hawes is published by Channel 4 Books, price £14.99. Cannibal, a three-part television documentary, starts on Channel 4, on Tuesday at 10pm