Not everyone was of the same opinion. In a street behind the London Assembly building, scores of pro-republican campaigners had gathered, waving placards reading: "Make monarchy history" and "Don't jubilee-ve it" and chanting "Monarchy out, republic in." Today though, they seemed resigned to the fact that they were well and truly in the minority.
As the queen's barge approached and Tower Bridge lifted in salute, red white and blue streamers were tossed from the crowd. And then, as if on cue, the heavens opened, rain lashing those gathered on the riverbanks below.
Hoods and umbrellas went up, coats and ponchos went on, quickly followed by shouts of "brolleys down" from those behind.
Some of those who had gathered fled to shelter, but others remained determined to see out the whole seven-mile flotilla, even in torrential rain.
Patrick Gunning had been waiting for the flotilla since 11 a.m. on Sunday. It was well worth the wait, he said. "I've had my son Saul, who's 8, on my shoulders so we saw the whole thing, and we'll be staying a little longer."
London's Metropolitan Police said as many as 6,000 extra officers were on patrol during jubilee events.
The huge security operation comes as London prepares to host the 2012 Olympic Games, which open in late July.
Outside the capital, Britons gathered for thousands of jubilee-themed street parties and barbecues Sunday. Stores have been filled for weeks with an array of patriotic paraphernalia, from flag-adorned teapots to aprons to picnic sets, to help hosts set the scene for what is billed as a national celebration.
The celebrations continue on Monday and Tuesday, which have been declared public holidays to mark the diamond jubilee.
An afternoon garden party at Buckingham Palace will be followed Monday evening by a televised pop concert outside the palace grounds.
At the end of the concert, the queen will take to the stage to light the "National Beacon," which will be on the Mall. She will use a diamond made from crystal glass, which has been on display at the Tower of London from the beginning of May, to light the flame.
More than 4,000 beacons will then be lit in communities throughout the United Kingdom, along with the Commonwealth and UK Overseas Territories.
Tuesday will be a day of pomp and ceremony, as the queen attends a service of thanksgiving at St. Paul's Cathedral, followed after lunch in Westminster by a carriage procession back to Buckingham Palace, where she will appear on the balcony, flanked by members of the royal family.