Gesturing toward a patch of mud-encrusted pavement in front of a sweetcorn stall, the old man says: "They brought the head here. They went to his home and got him. It was a warning to the others."

Dominic Njinu's mutilated torso was found by children in bushes 500 metres from his home last month. His head was left at Kiambu bus station, a short drive north of Nairobi, where he had worked as a minibus tout.