Humanity gets its vegetable calories mostly from three crops: maize, wheat and rice, in that order. But as the changing climate makes them harder to grow, a fourth – cassava – may out-perform them all.

Just one snag: it’s extremely poisonous.

When chewed it releases powerful toxins, including cyanide. 10,000 year ago the inhabitants of Amazonia developed a way of detoxifying cassava tubers by a laborious process of shredding, soaking, drying and grinding. Since then the crop has spread to many hot countries, becoming a staple in Africa, India and East Asia as well as its native Brazil.

You may have eaten it already in the form of tapioca (which made a cheap, satisfying pudding in my post-war schooldays). You may eat a lot more of it in years to come.