Helen Madide: Acquitted but guilt-ridden

While the couple tried to sort out their differences, Helen returned to her parents' village. Baby Fulufhuwani regularly went to stay with his father and grandmother.

While most of the 70,000 sangomas in South Africa provide herbal remedies for minor ailments, some crave more potent ingredients to practice muti, the Zulu word for medicine.

"He began to tell me stories. His ancestors said that he must kill me and the child so that he can be rich," Helen told Nobody's Child, a BBC documentary on the investigation into the London boy's death.

"He showed me the path and forced me to go along that path. He was pushing me and demanding me to go whether I like it or not. He said he was going to kill the baby first while I see the baby, then secondly he will kill me."

Although Helen tried to escape, Mabuda caught her and forced her to hold Fulufhuwani's legs while he cut the child's throat.

"When the child was dead, he started to cut all those pieces, the hands, the legs and even the sex organs," Helen says.

Limbs from children, primarily the sexual organs, are said to be the most potent. These are sometimes taken from live victims because their screams are thought to enhance the power of the medicines.

A police graphic of the child's remains found in the Thames

Mabuda then locked Helen up with the child's body. But his relatives, fearing for his wife and child, called the police.

Although her husband was sentenced to life in prison, Helen was acquitted. Six years after her child's death, Helen is trying to get into university to study human sciences.

She has been accepted at a number of universities but the offer is always withdrawn when they realise she is that Helen Madide. One university refused to provide her with accommodation because they feared she might be a danger to local children.

Butchered innocence

Conservative estimates are that at least 300 people have been murdered for their body parts in the past decade in South Africa.

And Dr Anthony Minnar, of the Institute for Human Rights and Criminal Justice in South Africa, fears the toll could be much higher.

Jeffery Mkhonto had his genitals cut off at age 12

"We have children going missing every week from our townships," he says. "The assumption is that those missing children are being put into prostitution and also that they are being used for muti murder."

One of the few who lived to tell the tales was Jeffery Mkhonto, who four years ago when he was 12 was mutilated by an organised gang sent to harvest body parts.

Jeffery was called over to the house of a neighbour for some food. Instead the man cut off his genitals with a butcher's knife.

"They took me home and left me in front of my father's house. As they left I heard them say they are going to sell my parts so that they can get money."

I heard them say they are going to sell my parts so that they can get money

Jeffery Mkhonto

But the police have found it difficult to investigate because in such cases, no-one is prepared to come forward.

Similarly in London, little progress has been made on identifying the torso of the boy which was found in the Thames last September - or his killers. Whether or not he was indeed the UK's first recorded victim of a muti killing, the Metropolitan Police are convinced it was ritualistic.

Among the South African experts advising them is Colonel Jonker, who has retired from that country's Occult Crime Unit.

He says: "If there's a guy operating in London, he's going to need body parts again."