And the country's former president, Nelson Mandela, has agreed to help by appealing for clues to the killing.

We're using Mr Mandela to reach out to those who perhaps would not normally have listened to the appeal in the UK

Det Insp Will O'Reilly

The boy is black and was estimated to be about five or six years old.

A pathologist report and DNA tests suggested he was from the African continent.

And ongoing "bone mapping" tests on his body will help to pinpoint the country and region where he lived and grew up.

No-one fitting the boy's description has been reported missing in the UK or Europe.

Voodoo

One of the detectives, Detective Inspector Will O'Reilly, told BBC Radio 4's Today programme: "The trip is two-fold, really. First of all, it's to learn from the experience of the South African police who investigate these sort of murders and they have a occult group set up just to do this.

"And second, of course, Mr Mandela is a highly respected and valued person throughout the whole of the African community.

"We now believe this child may have come from Africa and so we're using Mr Mandela to reach out to those who perhaps would not normally have listened to the appeal in the UK."

The boy may have been a human sacrifice

'Muti' killing is a human sacrifice practiced in southern Africa and voodoo killings are in western Africa.

Police believe the possibility the boy may have been the victim of a paedophile or stranger is now more remote.

Detectives investigating the murder are continuing to appeal for witnesses and a �50,000 reward has been offered for information.

Call the police incident room on 0208 853 1212.