Parasitic worms, endemic across Africa, form an obstacle to education. Lodged inside the digestive systems of one third of local children, they cause dreadful abdominal pain (not to mention anaemia and stunted growth) accounting for one quarter of all school absenteeism. The cost of de-worming tablets taken twice yearly is 5p per child. Repeat: 5p per child. It’s not often you get the chance to help a whole schoolful of children for £28.