The British have always been good at silence ˜ at family meals spent wordlessly; intense emotions expressed through a hand on the shoulder ˜ but on Sept. 6, 1997, they surpassed themselves. London, the big, braying capital, was stilled as over a million mourners of Diana, Princess of Wales, kept vigil along the route to Westminster Abbey. The hush amplified the sounds of the cortège as it set out from Kensington Palace: the rumble of wheels on tarmac, the clopping of horses' hooves, and a bell that tolled at listless intervals. But as the procession came into view, turning out of the palace gates onto the public road, a shriek pierced the morning air:"Diana, my Diana!" and then a despairing wail:"We love you, Diana!" Britain's customary stoicism had been overwhelmed by raw, unbridled grief.

It has become commonplace in the decade since Diana's death on Aug. 31, 1997, to say that the festival of mourning which culminated in her extraordinary funeral marked a transformation -- the moment when the old British virtues of reserve and silent suffering, of"mustn't grumble" and" could be worse," gave way to publicly expressed catharsis. The People's Princess had unlocked hearts, reordered values, presided at the triumph of emotional intelligence over cold intellect, of compassion over tradition.

The truth is harder to pin down, as tricky as the Princess herself could be. If Diana mattered, her significance rests in a series of interlocking social and political revolutions in a nation with a disproportionate impact on global culture, high and low -- revolutions in which she participated, part unwitting catalyst, part canny activist....