Britain has begun four days of festivities for Queen Elizabeth II's diamond jubilee, with organisers hoping a surge in enthusiasm for the royals will inspire crowds to defy drizzling rain.
Gun salutes around the country kicked off celebrations at 1200 GMT on Saturday, marking the exact anniversary of the queen's coronation, while the sovereign herself was to indulge her love of horse racing at the Epsom Derby.
"It's not every morning you wake up on a day that will be written about in the history books," declared the Sun, Britain's bestselling newspaper.
"Make the most of this once-in-a-lifetime occasion. It may be centuries before another comes along."
London was festooned with flags and bunting amid the highest support for the royal family in decades, with a recent poll showing that about 80 per cent of Britons want the country to remain a monarchy.
A huge pageant of about 1,000 boats will sail through London on Sunday with the 86-year-old queen in a special royal barge.
Thousands of street parties are planned around the country, although forecasters were predicting heavy rain throughout the day.
About 4,000 beacons will be lit on Monday across the Commonwealth following a huge picnic and star-studded concert at Buckingham Palace.
Tuesday is devoted to ceremonial events including a thanksgiving service and carriage procession.
Monday and Tuesday will form a rare double public holiday.
Political leaders lined up ahead of the celebrations to praise the queen, who in 60 years on the throne has won a reputation for shrewdness and devotion to duty, an unflappable demeanour and a seemingly infinite collection of hats.
Prime Minister David Cameron said in a video tribute: "I think it's hugely important. The queen has given incredible service - 60 years on the throne, a lifetime of service - she's never put a foot wrong.
"She's hugely popular and respected, and it's an opportunity for people to give thanks and say thank you."
On Saturday, 72 horses and six World War I-era 13-pounder gun carriages were to head for parade grounds in central London after taking part in a morning procession.
Their 41-gun salute will be accompanied by other salutes around the country, including at the 900-year-old Tower of London.
The queen, an avid horse-racing fan who still rides despite her age, has attended the Epsom Derby, Britain's richest equine race, which dates back to 1780.
She was driven down the course in an open-topped vehicle before a flag-waving crowd of an estimated 150,000, after a display from the Red Arrows aerobatic team and performance of the national anthem by soprano Katherine Jenkins.
Across the UK, red, white and blue "Union Jack" flags billowed from street lamps, shop fronts and houses, and sales of patriotic souvenirs rocketed ahead of the celebrations.
Millions of people are also expected to attend street parties across the country as surveys of public opinion show the royal family's popularity is as high as it has been for decades.
In the Telegraph newspaper, Michael Lockett, chief executive of the Thames Diamond Jubilee Foundation, said the rain should not stop the nation taking the chance to "be part of history".
"In these austere times, we need cheering up more than ever," he said.
The queen acceded to the throne on February 6, 1952, upon the death of her father King George VI while she was away in Kenya, and was crowned the following year on June 2.
Royal watchers recalled it had also poured with rain on the day of the queen's coronation.