John De Carteret has already taken a call about three captured Asian hornets when we meet on a gloriously sunny morning on the Channel Island of Jersey. The retired police forensics detective is the linchpin of the Jersey Asian Hornet Group (JAHG), a band of two dozen volunteers. These mostly retirees are the frontline troops in a seemingly unwinnable war against an invasive foe – a voracious predator of honeybees and all other flying insects, which has rapidly conquered the west European mainland. But De Carteret, who sports a JAHG polo-shirt and a lanyard showing he is authorised by the...