Of all the mysteries of ancient Rome, silphium is among the most intriguing. Romans loved the herb as much as we love chocolate. They used silphium as perfume, as medicine, as an aphrodisiac and turned it into a condiment, called laser, that they poured on to almost every dish. It was so valuable that Julius Caesar stashed more than half a tonne in his treasury.

Yet it became extinct less than a century later, by the time of Nero, and for nearly 2,000 years people have puzzled over the cause. Researchers now believe it was the first victim of man-made climate change – and warn that we should heed the lesson of silphium or risk losing plants that are the basis of many modern flavours.