“History is best told as a story of organised crime,” Kemp says. “It is one group creating a monopoly on resources through the use of violence over a certain territory and population.”

History shows that increasing wealth inequality consistently precedes collapse, says Kemp, from the Classical Lowland Maya to the Han dynasty in China and the Western Roman empire. He also points out that for the citizens of early rapacious regimes, collapse often improved their lives because they were freed from domination and taxation and returned to farming. “After the fall of Rome, people actually got taller and healthier,” he says.

“Last but not least is that, unfortunately, all the threats we face today are far worse than in the past,” he says. Past climatic changes that precipitated collapses, for example, usually involved a temperature change of 1C at a regional level. Today, we face 3C globally. There are also about 10,000 nuclear weapons, technologies such as artificial intelligence and killer robots and engineered pandemics, all sources of catastrophic global risk.

Maybe true, but without a timeline it is just a source of anxiety.