“We don’t want another Diana.” Thus runs a mantra among Britain’s royal family, whose more retiring members—most notably Queen Elizabeth II—harbor a deep fear of scandal. Yet, as Brown’s account opens, scandal and controversy emerge as the coin of the realm, in this case with the brouhaha surrounding Prince Harry’s marriage to Meghan Markle, marked by “the Palace’s inaction at her character assassination by the press.” As the author remarks, the royal family, headed by a 96-year-old with a 74-year-old waiting to assume the throne, “cannot be expected to be nimble.” Indeed, many of its members are downright boring, if dutiful, in contrast with rebels such as Diana and Meghan, to say nothing of disgraced figures such as Andrew and Fergie. In the case of Diana’s gruesome death, writes Brown, “the Queen’s usual impeccable sense of how to do the right thing…was beset by the need for a new kind of emotional response that met the moment of the crisis,” which Elizabeth couldn’t muster. Indeed...