They are called the Nose Jury and their olfactory senses are to waste treatment what Betty Grable’s legs were to cinema – vital tools for delivering customer satisfaction.

In the Suez Environnement research centre outside Paris, a group of trained sniffers is taking a “nose break”, between bouts of inhaling air samples collected from water and waste treatment sites around the country. Their fine sense of smell will pick up traces of odorous molecules and identify whether they bring to mind a pleasant pine forest or the stench of dead ­animals.