Over the last four years, at least 400 African children have been abducted and trafficked to the UK and rescued by the British authorities, according to figures obtained by the BBC. It is unclear how they are smuggled into the country but a sinister picture is emerging of why.
Whether it is through leaflets handed out in High Streets or small ads in local newspapers, witch-doctors and traditional African spiritual healers are becoming ever more prominent in Britain.
The work many of them do is harmless enough, but there is evidence that some are involved in the abuse of children who have been abducted from their families in Africa, and trafficked to the UK.
According to Christine Beddoe, director of the anti-trafficking charity Ecpat UK, a cultural belief in the power of human blood in so-called juju rituals is playing a part in the demand for African children.
"Our experience tells us that traffickers can be anybody. They can be people with power, people with money or people involved in witchcraft," she explains.
"Trafficking can involve witch-doctors and other types of professionals in the community who are using those practices."
Violent and degrading
Figures compiled by Ecpat, combined with those of the Metropolitan Police and Ceop, the Child Exploitation and Online Protection Centre, show that at least 400 African children have been abducted and trafficked to the UK and rescued by the British authorities.
Testimonies from many of these children have revealed that once they arrive in Britain, they are exposed to violent and degrading treatments, often involving the forced extraction of their blood to be used for clients demanding blood rituals.
Some of these victims agreed to share their experiences on the promise of anonymity because they still fear their abusers.
One boy explained how witch-doctors took his blood to be used in such rituals: "The traffickers or witch-doctors take your hair and cut your arms, legs, heads and genitals and collect the blood. They say if you speak out I can kill you."
Another victim feared for her life, saying the "witch-doctor told me that one day he would need my head.
"Sometimes I would wake up and he would be standing over me with a knife, every night I was terrified that he would do it."
Meanwhile, a girl from Nigeria remains convinced the spell performed on her means she can never identify her traffickers, for fear her family will die.
"They told me I was evil and made bad things happen. I believed it and that this was my punishment and what my life would be."
Human blood ritual
Witch-doctors, or traditional spiritual healers as they prefer to be known, are becoming more prominent in Britain.
Many offer "life changing rituals", involving prayer and herbs. A price tag of £350 ($547) would not be uncommon.
But there are some who engage in more sinister practices.
Posing as a couple with financial problems, I visited 10 witch-doctors. All offered herbal potions to end our money worries, but two also made the offer of a ritual involving human blood.
Although, there is no evidence that they themselves were involved in the trafficking and abuse of children, it contributes to a disturbing picture of abduction and abuse.
According to a US State Department report, Uganda has become one of the main source countries for children to be bought and smuggled to Britain. Some 9,000 children have gone missing in the country over the past four years.
The ease with which a child could be procured was apparent when, posing as a British trafficker, I went looking for help in the cafes and bars in the underworld of the Ugandan capital, Kampala.
For $250 (£160) a reformed criminal introduced us to Yunus Kabul, who boasted he had been abducting children for witch-doctors in Africa and abroad, for years.
During our conversation he offered as many children as we required.
"I have enough, a hundred, no problem. I have so many communications. I have a network across whole of Uganda."
Mr Kabul arranged a meeting at an isolated hotel. Unaware he was being recorded, he described how he got hold of children for his customers.
"It all depends how they want it done? I can take you to a family home, I would have no problem to get a child officially or there is a way of doing it secretly, abduct a child."
I asked Mr Kabul if the police would cause a problem.
"I have to find a house where we can take the supply, the children, in a remote area. So the police cannot find them," he explained.
Mr Kabul demanded a fee of £10,000 ($15,600) per child. I withdrew from the negotiations.
The head of Uganda's Anti-Human Sacrifice Police Task Force, Commissioner Bignoa Moses, admits there is a problem: "We cannot rule out that children end up abroad because as of now we don't have the capacity to monitor each individual and many simply disappear."
Back in the UK, despite the testimony of so many victims, the cultural belief in the power of juju is a huge challenge for the authorities.
One senior police detective says part of the problem is the silence that surrounds the matter.
"While juju is widely believed, it is rarely spoken about publicly. People think even talking about juju might lead to something bad happening to them," says Det Ch Supt Richard Martin, head of the Metropolitan Police's Human Exploitation and Organised Crime Command.
"This presents officers with enormous difficulties when it comes to investigating these crimes and bringing the perpetrators to justice."