ASTONISHINGLY, 430 people responded to Armin Meiwes's online advertisement for a ''well-built man, 18-30 years old, for slaughter''. Not all of them wanted to die. Some of them were hoaxers. Most of them just wanted to play out a sexual fantasy. Four men were so interested, they travelled to Meiwes's country home in Rotenburg, a small town in central Germany, to meet him. When Meiwes discovered the men, including one from London, wanted to role-play and nothing more, he turned them away, bored.

Bernd-Juergen Brandes was different. He wanted to be eaten and to even eat parts of himself. ''I offer myself to you and will let you dine from my live body. Not butchery, dining!! Whoever REALLY wants to do it will need a REAL VICTIM!!'' he wrote in an online chatroom. He told Meiwes he was a ''devoted pig for slaughter''.

Needless to say, this is not the kind of cannibalism we associate with distant lost tribes or the desperate, last-resort cannibalism of stranded plane-crash victims. Cannibalistic fetishes are uncommon, according to Dr Keith Ashcroft, an Edinburgh-based forensic psychologist. It is, therefore, extremely rare for someone to be as determined as Brandes was for such a fantasy to become reality.

So far, observers of Meiwes's trial in Germany have given a variety of reasons why, on March 9, 2001, Brandes, a well-paid 43-year-old microchip engineer from Berlin, took the day off work and bought a one-way ticket to visit Meiwes, to be slaughtered and eaten.

According to some psychiatrists, he was irrevocably damaged by the death of his mother in a car crash, for which he blamed himself. Such a gruesome death would be satisfactory punishment. Others concentrate on the apparent sexual nature of the murder. In Meiwes's specially prepared slaughter room, he recalled in court, Brandes asked Meiwis to cut off his penis. Meiwes later cooked it and the pair ate it together.

Some men choose to have their genitalia removed as part of a fetish, an extreme sado-masochistic fantasy that involves the cooking and consumption of testicles. To understand this apparently consensual murder, however, Aschroft asserts that it is helpful to understand Body Dysmorphic Disorder, which one source describes as ''a mental disorder related to Obsessive Compulsive Disorder''. Aschcroft says: ''The

victim is likely to have BDD. He wanted his body to be destroyed. Other people who have it will do things like lying on a railway track with their legs over the edge so that their legs are taken off, '' he says.

''BDD is an extremely serious illness. Part of it is disassociation, where the person doesn't feel connected to the body and doesn't feel connected to the world, to the extent that they actually don't feel pain. It is, in an extreme sense, similar to self-harm, when people cut themselves to feel better, to feel great, to feel real again. If this was his disorder, Brandes was enjoying what was happening to him.''

There is a consensus that - whether it was because he was depressed, ill, or delusional - Brandes, above all, wanted to die. ''Maybe for him, it was just an interesting

way to go,'' says Ian Hancock, director of psychological services in Dumfries and Galloway.

''We can only hypothesise, but perhaps he wanted to die anyway, and he was looking for the ultimate masochism, a sexually exhilarating experience. On the part of the cannibal, however, it is less easy to

simply conclude there was a huge sexual element. It may well be that, for him, this fulfilled a whole range of fantasies - violent rather than

sexual,'' he says.

The murder certainly seems sexually motivated at first glance. Indeed, Meiwes, a 42-year-old who also worked in computers, is being tried for ''murder for sexual satisfaction''. ''How festishes escalate as they perhaps did in Meiwes's case is unknown,'' says Ashcroft. ''What is certain is that it is extreme, and it doesn't bring anything good to anyone. It's a horrible anxiety - like any fetishes are, whether for shoes or anything else - that brings stress and worry. There is no joy in it.''

Meiwes himself talks of a sense of power he felt after stabbing his victim, cutting his body, and storing it to eat at a later date. He, too, had a difficult relationship with his mother, describing her as ''domineering''. He dreamed of having a little brother, ''to become part of me'', he said.

Rudolf Egg, a criminal psychologist at the Criminal Institute in Germany, interprets Meiwes's act as a way of compensating for his lack of close relationships. He said: ''When you have sex with someone, you have a very high level of personal contact with them. Sexual cannibalism is just a more extreme version; it is the highest form of intimate behaviour.''

''It is also likely that the pair also had a kind of thought and action fusion,'' says Ashcroft. ''A kind of magical thinking, where they have thought about something so much that it becomes real, and they bring it into reality. We might want to

own a Rolls-Royce, but we don't

do everything we can to get it.

That's the difference between them and us.''

Claims in German tabloid newspapers that the murder was satanic, based on the fact that Meiwes's mother was a witch who murdered ''at the order of Satan'', have been uniformly dismissed. Several commentators have made much of his description of eating Brandes's remains as being ''like taking communion'' in a religious service, although this, too, has been dismissed as mere metaphorical expression, rather than an indication that his actions presented some kind of spiritual experience.

While an innately intriguing subject, Meiwes's and Brandes's mutual hunt for gratification adds an extra fascination for the ever gory-hungry public. While many with no interest in cannibalism may pass through cannibalistic forums as they idly surf the net, Ashcroft fears the forming of more serious, purposeful online communities. (Similar to those that provide online support for anorexics, which seek to encourage sufferers to cling to their condition, rather than recover from it.) The Cannibal Cafe on www.necrobabes.org, a site similar to the one on which Meiwes posted his advertisement, is temporarily closed, but such forums are plentiful. Without them, Meiwes and Brandes almost certainly would never have met.

Keith Ashcroft adds: ''It is horrendous and deeply worrying that the internet can gather people together to form such destructive acquaintances. People who are lonely and depressed can now easily find people who are the same and encourage one another, and it can only be disastrous. In this case, it was fatal that these two people were able to meet . Until more recently, cannibalism has been one of those taboos, and thank God we do still have those taboos that separates us from animals. The internet, worryingly so, is diminishing them.''

On the other hand, without such cases, we would never have the opportunity to prove our moral

stability. All nodded and approved in October, when a group in Nabutautau, a remote Fijian village, apologised on behalf of their cannibal ancestors who murdered and ate Rev Thomas Baker, a British Methodist missionary. Equally, all gasped in horror when refugees

fleeing North Korea reported this summer that cannibalism is increasing in the country, following poor harvests and cuts in international food aid.

''The reason we respond to cannibalism so strongly is that it is such a rare thing: we must remember that,'' says Hancock. ''When we think of cannibalism, we think of ancient tribes, Hannibal Lecter, and the film, Alive. In this case, we will be shocked and intrigued in the same way we are intrigued by serial murders. Such cases will continue to sell papers, books and cinema tickets, all the more because it is true.''