Earlier, gun salutes were held in London, Edinburgh, Cardiff and Belfast to make the anniversary of the coronation in 1953.
Only one British monarch has spent longer than the current queen on the throne: Victoria, who reigned from 1837 to 1901. Her Diamond Jubilee in 1897, captured on grainy black-and-white film, is the only precedent for this weekend's events. It's just over a year since London's streets saw the last major royal event, the marriage of the queen's grandson, Prince William, to Kate Middleton.
"For 60 years the queen has been a point of light in our national life; brilliant, enduring and resilient," Prime Minister David Cameron wrote in a tribute to the monarch this week for Parliament's The House magazine. "Through a reign of unparalleled change - from postwar Britain through to the jet age, space age and digital age - she has remained resolutely unchanged in her commitment to this country."
The queen - the 40th monarch in a line that began with William the Conqueror in 1066 - took the throne at a time when Britain was recovering from the ravages of World War II, with food rationing still in force, and beginning to grant independence to its colonies. Winston Churchill, who'd led the country to wartime victory, was again prime minister, the first of 12 who've held weekly audiences with the monarch.
Saturday's big race at Epsom is an appropriate way for the jubilee weekend to start. Owning and breeding racehorses is one of the queen's main interests, though she's never won the Derby.
Sunday, the focus switches to the River Thames, when the queen will join a flotilla of more than 1,000 vessels for the Diamond Jubilee Pageant.
The following evening, there will be a concert outside Buckingham Palace, the monarch's central London residence, featuring stars such as Paul McCartney, Elton John and Tom Jones - all of whom have been knighted by the queen.
The final day of the celebrations will see the queen and the extended royal family attending the national service of thanksgiving at St. Paul's in London's financial district on June 5.
After a reception at the Mansion House hosted by the Lord Mayor of London and lunch at the Houses of Parliament, the queen and Prince Philip will return to Buckingham Palace in a horse- drawn open carriage. The heir to the throne, Prince Charles, and his wife Camilla will also be in the procession, along with William and his wife and William's brother, Prince Harry.
The climax of the event, just before 3:30 p.m., will see those senior royals appear on the palace balcony, in time for a flypast by planes of the Royal Air Force and a celebratory cascade of rifle fire from the soldiers of the Queen's Guard, interspersed with the national anthem.
A YouGov poll conducted May 27 and May 28 found 86 percent of 1,743 respondents saying the queen had done a good job as monarch. Of those surveyed, 73 percent said Britain should continue to have a monarchy, up four points on a year ago.
"It's only really been over the last five, eight, 10 years that I've really learned to understand and accept the huge deal that she is around the world," Harry said in an ABC television interview that aired this week. "She has managed to get the family to move with the times."
The queen has weathered less popular times. Many found her response to the 1997 death of Princess Diana, an internationally popular figure before and after the breakup of her marriage to Prince Charles, to be cold and indifferent to the outpouring of public grief. "Show Us You Care," shouted a headline in the Express newspaper before the queen broke days of silence over the tragedy.
Cameron, interviewed by Sky News television Friday, was asked whether he thought the queen might step down in favor of her son, Prince Charles.
"I wouldn't anticipate that," he replied. "What I see in Her Majesty is someone, in spite of the fact she's been on the throne for 60 years, in spite of the fact that her and Prince Philip are now relatively elderly, there is an extraordinary level of physical energy, mental energy, and above all devotion to her people, to the institutions of this country, to the way our democracy works."
Paying his own jubilee tribute to the queen, the head of the Church of England, Archbishop of Canterbury Rowan Williams, spoke of her sense of humor in their one-to-one meetings.
"I found in the queen someone who can be friendly, who can be informal, who can be extremely funny in private - and not everybody appreciates just how funny she can be - who is quite prepared to tease and to be teased, and who, while retaining her dignity always, doesn't stand on her dignity in a conversation," he said in a video released by his office.
The celebrations may do little to help the economy, with spending on food and drink and tourist revenue likely to be offset by a loss of output as some companies shut down for the entire week.