Greta Thunberg’s great American adventure has begun. Last Wednesday, she set sail from Plymouth like the pilgrims did, her Mayflower a zero-carbon but very expensive racing yacht; her goal not religious liberty but a camera-rich turn at the UN’s climate change conference in New York.

Meanwhile, on dry land, GQ magazine recently appointed Greta its “game changer of the year”, with a cover image in which the teenager, whether she realises it or not, strikes a stern, finger-pointing pose reminiscent of Lord Kitchener’s First World War recruiting poster and tells Britain’s feckless carbon-emitters: “To do your best is no longer good enough.”

Greta is just an ordinary 16-year-old Swedish schoolgirl whose fiery visions have convinced the parliaments of Britain and Ireland to declare a