LONDON — Braving a day of bone-chilling, rain-dampened weather, a crowd estimated by the police at more than a million people lined the banks of the Thames on Sunday to acclaim Queen Elizabeth II as she marked 60 years on the throne with a royal river pageant of a kind last seen 350 years ago.

The stirring flotilla of a thousand boats, the highlight of a four-day holiday to celebrate the monarch’s diamond jubilee, combined with the familiar miseries of the British climate to produce a vignette that some embraced as a demonstration in minor key of the character of Elizabeth’s reign: unflappable steadiness. 

The monarch, who is 86, and her husband, Prince Philip, 90, never donned coats through the hours they spent on the open deck of the royal barge as it made its way down the seven-mile course of the pageant, waving at crowds that shouted “God save the queen” and hoisted a forest of plastic Union Jacks. Neither did they sit in the thronelike red velvet chairs set in the prow, apparently reluctant to claim a luxury not available to the onlookers....