When Germany invaded the Isle of Sark—the last foothold of feudalism in the western world—Dame Sibyl Hathaway protected her people with the unlikeliest of weapons: Feudal etiquette, old-world manners, and a dollop of classic snobbery. Dame Sibyl Hathaway had 275 Nazi prisoners on her hands and knew exactly what she wanted to do with them. It was May 1945. Five years earlier, Germany had invaded Hathaway’s home in the British Channel Islands, a tiny isle of 400 called Sark. Despite having no modern defense network or fancy gun emplacements—it didn’t even have electricity—Sark had proven itself to be uniquely prepared...