The most obvious red herring. One of the most popular theories regarding Napoleon Bonaparte’s death is that he suffered arsenic poisoning from the green colouration in the wallpaper of the bedroom of the place in which he was being held. It has been suggested that microbes, present in the humid conditions of St Helena, could absorb the poison from the wallpaper, then be inhaled by the prisoner, giving him a small dose every day. The wallpaper is green, and the pigment involved is copper arsenite, known in Napoleon’s day as “Paris Green”.