(Reuters) - Britain's Queen Elizabeth joins an armada of 1,000 boats in a gilded royal barge down London's River Thames on Sunday in a spectacular highlight of four days of nationwide celebrations to mark her 60th year on the throne.
Hundreds of thousands of people waving "Union Jack" flags and dressed in red, white and blue braved the wind and rain to line the 7-mile (11 km) route for one of the largest flotillas ever seen on the river.
Up and down the country, millions more were due to attend diamond jubilee street parties over the long holiday weekend in honour of the 86-year-old queen, the only British monarch after Queen Victoria to have sat on the throne for 60 years.
Leisure cruisers, rowing boats, yachts and canoes made up the colourful Thames armada that also features vessels from the 1940 evacuation of British and Allied troops from Dunkirk in northern France, a famous rescue performed by crafts of all shapes and sizes and a celebrated piece of British history.
A typically inclement British summer's day failed to dampen enthusiasm, with boisterous crowds five people deep massed along the banks of the Thames, watching giant TV screens showing black-and-white images of the queen from her childhood.
"We're English, we know what the weather is like. We really don't care if we get wet you know - it's the jubilee, it's the queen, so it's nice to come up and celebrate it," said Jackie, a 39-year-old sales consultant who travelled across southern England to watch the event.
Organisers say Sunday's river pageant is the largest of its kind in 350 years since a similar spectacle was held for King Charles II and his consort Catherine of Braganza in 1662.
A floating belfry with a set of eight church bells specially cast for the celebrations will be at the head, with bells from riverside churches pealing out as it passes by.
The queen will be on board "The Spirit of Chartwell", a barge adorned with flowers, together with her 90-year-old husband Prince Philip and other members of the royal family including heir-to-the-throne Prince Charles, his eldest son Prince William and new wife Kate.
CHURCHILL AND EISENHOWER
Other vessels include Motor Torpedo Boat 102 on which Allied Forces commander General Dwight Eisenhower and British Prime Minister Winston Churchill inspected warships before the 1944 D-Day invasion of Nazi-occupied France.
The flotilla will travel under 14 bridges and past landmarks including the Houses of Parliament, St Paul's Cathedral, and the Tower of London.
"It's a pageant and there haven't been pageants like this on the River Thames for 300 years and that makes it extremely special," said Peter Warwick on board "The Macaret" launch.
"You look at the river banks and they are packed with people -- thousands of people watching this happening."
Another boat taking part, "Amazon", also featured in diamond jubilee celebrations for Queen Victoria, Elizabeth's great-great-grandmother, held in 1897 when Britain's empire spanned much of the globe.
Although the queen is still head of state in 16 countries from Australia and Canada to tiny Tuvalu in the Pacific Ocean, Britain is now a shadow of its former imperial self.
Historians and commentators say the pomp and spectacle of British royal occasions gives the country a sense of national pride at a time when the economy is in recession and people face deep austerity measures.
Across , Scotland, Wales and Northern Ireland, street parties were being held to mark the occasion. Prince Charles and his wife Camilla dropped into one in central London before the pageant, joining in a rousing rendition of the national anthem.
The government hope the festivities will mark the start of a summer of revelry capped off by the Olympic Games in London, raising the public's spirits and their own poll ratings.
"What is great is that we have the jubilee and then the Olympics. We should show how great we are in Britain," said Joanne Richmond, 61, from central England, who was in London for the queen's coronation as a two-year-old.
However, economists have warned that the extra public holidays will hit Britain's already ailing economy, potentially prolonging a recession.
WILLIAM AND KATE WEDDING
The celebrations come as polls show the overwhelming backing for the monarchy, which has overcome a slump in the 1990s following marital infidelities and the death of the hugely popular Princess Diana in a 1997 Paris car crash.
Last year's wedding of Prince William to Kate Middleton was proof of such enduring appeal with the ceremonial extravaganza attracting a global audience of up to two billion people.
However, not everyone in London will be cheering. The small yet vocal republican movement plans a protest during the flotilla, saying the jubilee was "a celebration of inherited power and privilege, and those celebrations have no place in a modern democracy".
But even they acknowledge there is almost no chance that the queen will be ousted and take solace in indications many Britons are simply indifferent -- 2 million people are leaving the country to take advantage of the extended public holiday.
"Some people will hate this day, some think it is a waste of taxpayer money, but I think the queen has been a great leader and the royal family brings a lot of tourism to England," said Rachel Harrison, 41, her face painted with a Union Jack.
Celebrations will continue on Monday with a pop concert outside Elizabeth's London residence Buckingham Palace, where Paul McCartney and Stevie Wonder will be among the acts. Madness are set to take to the roof of the famous landmark to belt out hit song "Our House".
The long weekend concludes with a service of thanksgiving at St. Paul's Cathedral on Tuesday followed by a carriage procession along the broad Mall leading to Buckingham Palace where the queen will wave to the crowds from the balcony.