The Black Death, the bubonic plague that tore into England in 1348, was — this should not need saying — a cataclysm. The English had little natural immunity to this terrible disease, which arrived in Europe with the Mongols, either making its debut or for the first time in thousands of years. About 80 percent of those infected died. By the end of this first great wave of infection (others were to follow), England, like many other European countries, had lost around half its population…