Climb over the hill and head for the plateau. That, according to biologists, defines the path to extreme old age. Researchers announced last week that, once someone reaches 105, their chances of dying stop rising, start to level off and might even decline.

Similar “late-age mortality plateaux” have been found in insects, and hinted at in rodents, but the discovery of one in humans will excite controversy. If people essentially stop ageing after becoming centenarians, it is legitimate to ask: are there any natural limits to human lifespan?

This latest analysis was led by demographer Elisabetta Barbi, who scrutinised the hazard rates (measuring the likelihood of death) of all Italians aged 105 and above, who were living between 2009 and 2015. More than 3,800 Italians fell into this age group.