Several hundreds of them. But nobody has any clear idea as to their number. Nobody seems to care either. None has been prosecuted so far.
NGOs and human rights lawyers have sounded the alarm over the "invisible children," illegally smuggled into Britain using false visas and documents.
Dragan Nastic, Unicef UK's policy and parliamentary officer, said: "The first recognised case of child trafficking in the UK was a Nigerian girl more than 10 years ago in 1995. Here we are in 2007 and there have been no prosecutions made in cases of children trafficked into domestic labour from Africa. Not one."
Since 2003, 62 cases of child trafficking have been prosecuted, and there are 59 pending. The police do not break the statistics down in terms of ethnicity, but experts confirm that no prosecution has ever been made relating to African children.
Recent studies suggest that hundreds of children are brought over from African countries, such as Nigeria, Ghana and Uganda, by highly organised traffickers.
Nigeria is believed to be the main source country on the continent, where destitute families are either paid for their children or persuaded to give them away believing that they will receive an education and a better life in the UK.
On arrival, children as young as 10 are kept undercover from British society and forced to work as domestic slaves or prostitutes. Behind closed and often locked doors, they work long days for no money, are kept from school and beaten if the work is not done.
Tolu never wanted to leave her family in Nigeria but when her parents insisted she went to the UK for an education, she decided to do as they asked. At just 13, a stranger brought her over on a flight to London and took her to the family who were supposed to be looking after her.
But education could not have been further from her minders' thoughts. "They tricked my family, they told them I would be coming here to study," she said. "But when I arrived I was here to work and look after the children. I was so disappointed." Waking at seven every morning she had to cook breakfast for three children and take them to school, before getting on with the housework. "People used to ask me why I wasn't at school, but I was too afraid to say," she said.
The woman she worked for, that she refers to as her "auntie," was a well-to-do British Nigerian who worked in the Home Office. "She knew it was wrong," said Tolu, but that did not stop her from continuing to beat and bully her to work all hours at her beck and call. "It was like being in prison. At least in Nigeria I had freedom, even though we didn't have much."
After two years, the family finally registered her at a college but she was only allowed to go one evening a week. "because of all the work I had to do I was too tired to concentrate, and I failed the foundation maths exam twice."
She finally escaped at 19, after being severely beaten around the face for using the telephone to call a friend. She ran away while the couple were at work and is now applying for asylum.
The Home Office minister, Vernon Coaker, acknowledged that the Government still had a long way to go in tackling the issue of trafficked children from Africa. He said: "Research suggests that [trafficking] is not reducing in either scale or reach. It's a sad sign of our times that children are still being trafficked to the UK as modern slaves."
Mr. Coaker, who has been implementing the UK Action Plan on Tackling Human Trafficking, published earlier this year, said the practice was "a moral outrage," but it would take time for change to happen. "You can't change it overnight, but we [the Government] are also human beings, we also have children, and we're outraged that this happens. We'll do all we can to move this forward as quickly as possible."
The first report dedicated to child trafficking into the UK, published by the Home Office in June, showed that more than a third of the 330 children that were discovered to be either trafficked or suspected of being trafficked were African. The survey, which was undertaken over a 10-month period, revealed that 102 west and east African girls were discovered to have been trafficked into the country and enslaved.
And the authors of the report, the Child Exploitation and Online Protection Centre, acknowledge that this initial figure is "not a definitive number, but simply the cases that were brought to us in our initial study."
Christine Beddoe, director of Ecpat, a coalition of charities dealing with child trafficking, including the United Nations Children's Fund (UNICEF) and Save The Children, said that the Government's failure to prosecute the traffickers of African children was just one of the failures of the system.
She said the charity had found "a culture of disbelief in the offices looking at asylum claims," that caused escaped child slaves to be treated as illegal immigrants rather than unwitting, isolated victims.
According her African child slaves have become "the invisible children," passing by police, immigration and social services unnoticed. "Having suffered the most debilitating experience, they get no support," said Beddoe. "They are often here without a legal basis to stay, then are treated within the system as undeserving of help."
One of the main reasons why so many cases are disbelieved is the children have been given fake passports and identities, which contradict the true story they try to convey. Add to this a lack of training in recognising victims, and it becomes clear why many of these young people feel so let down by the police and social services they tried to turn to in the days after their escape.
Debbie Ariyo, director of Afruca (Africans Unite Against Child Abuse), said: "It's a scandal nobody has been convicted when we know so many people who have been trafficked and have lost their childhood.
"We're making a serious mistake in not convicting people, because it won't stop. How long can we go on for before someone is arrested and convicted? So many lives will be destroyed if urgent action is not taken."