Most African herbalists cause no more damage than dispensers of alternative medicines on our high streets. Every now and then, however, a sinister practitioner will advise a very special client that while roots and animal parts are useful, the most potent medicines are made from human blood, liver, spleen and heart. Yes, it is dreadful, he whispers, but there are unscrupulous people about, and I have heard that your rival is in the market for the stuff. What choice do you have? When one big man is persuaded, his peers are immediately alerted. In consequence medicine murders tend to crop up in clusters, the clients typically rich and powerful men. The anti-human sacrifice and trafficking unit of the Uganda police recorded 26 cases in 2008 and 28 in 2009, and a number of suspects were brought to trial.

Enter Tim Whewell of the BBC’s Crossing Continents programme. He found a Pentecostal preacher, Polino Angela, who claims to have murdered his own son and dozens of other children for potions. He has repented and is crusading against 'witch-doctors'. Curiously untroubled by the police, he tells Whewell that he hopes for an amnesty from the government. In the grand tradition of generations of British missionaries crusading against barbarism, Whewell follows the repentant Angela, in the garb of a Pentecostal prophet, as he traipses through the bush destroying ancestor shrines.

The BBC swallowed the dubious story whole, broadcasting it on Newsnight, and endorsing all sorts of bizarre rumours: 'it is widely believed' that bodies are buried under new buildings to ensure prosperity etc.

Whewell has his own theory about these horrors. Convinced, quite wrongly, that medicine murder is ‘something new', and that children are the preferred victims, he notes that paradoxically these horrors come 'just as Uganda is becoming more modern'. Perhaps, he reasons, it is actually connected to modernity – born of greed spawned by consumerism.

Medicine murders are rare – after all, only the very powerful can get away with them – but the poor have more immediate worries, and these are sometimes translated into fears of witches. At times of drought, war and disease, anti-witchcraft movements may sweep the countryside, now often led by Pentecostal preachers. (The individuals fingered by Angela for the BBC are at risk of vigilante violence.)

Whewell confuses belief in spirits with belief in witchcraft, and when a Ugandan cabinet minister tells him that evil spirits really do exist, he fails to register that this is a Christian doctrine, eagerly propagated by local and visiting preachers. The current priority of Uganda’s evangelicals is a crusade against homosexuality. Egged on by American activists, they have persuaded the government to draft a bill that imposes life imprisonment for homosexuality, and the death penalty for aggravated cases, such as the grooming of minors by school-teachers.

There are important stories here. Anthropologists and local intellectuals are following them closely. Our media should treat them with the same care as stories of child abuse in religious communities in Ireland or Jersey or the Orkneys.