Dr Hendrick Scholtz carried out a second post-mortem

Dr Scholtz said a human sacrifice would take place when a small group of people needed to obtain supernatural powers to be successful in areas such as business or politics.

Speaking about Adam, he said: "It is my opinion that the nature of the discovery of the body, features of the external examination including the nature of the wounds, clothing and mechanism of death are consistent with those of a ritual homicide as practised in Africa."

Detectives investigating the death are now looking at the ritualistic aspect as a major line of their inquiry, but not the only one.

They are also looking at a paedophile killing, a stranger killing, a mercy killing or domestic death.

A graphic depicting the boy in the orange shorts he was wearing when the body was found, has also been released.

Sheet and candles

The youngster's torso was spotted floating in the Thames by a man walking across Tower Bridge on 21 September last year. It had been in the water for up to 10 days.

Police have revealed they found seven half-burned candles wrapped in a white sheet washed up on the southern shore of the Thames in London.

The investigating officer, Detective Inspector Will O'Reilly, said the name found on the white sheet was a common name in the Yoruba area of Nigeria.

However, the police have been unable to trace anyone with that name in the UK.

Mr O'Reilly explained that ritualistic murders in South Africa have declined from about 30, 10 years ago, to three in the year 2000.

A reward of �50,000 has been offered for information leading to the conviction of Adam's killer.

Police have also been liaising closely with detectives in Germany and Belgium where three similar cases have emerged, involving the murder of children whose bodies were disposed of in running water.