Britain's Queen Elizabeth began her four-day diamond jubilee celebration Saturday watching horse races at the Epsom Downs course in southern England.

Many of the estimated 150,000 who gathered for the Epsom Derby were handed British flags to mark the milestone.

The celebration of the queen's 60 years on the throne officially began earlier Saturday with a 41-gun salute fired by the King's Troop, Royal Horse Artillery at the Horse Guards Parade site in central London.

Gun salutes also echoed in Windsor, Edinburgh, Cardiff and Belfast on the anniversary of her 1953 coronation.

On Sunday, she will sail the River Thames in a flotilla and attend a concert in the company of her family members and thousands of subjects.  At least 6,000 security guards will be deployed during the event.

On Monday, the 86-year-old monarch will light the national beacon while thousands of other beacons will be lit across the Commonwealth. On Tuesday, she and her husband, Prince Philip, are scheduled to attend a thanksgiving service at St. Paul's Cathedral.  The royal family will make a balcony appearance at Buckingham Palace Tuesday afternoon, wrapping up the four-day jubilee.

Elizabeth succeeded her father King George after his death in 1952 and was crowned the queen of the seven Commonwealth countries (the United Kingdom, Canada, Australia, New Zealand, South Africa, Pakistan, and Ceylon, now known as Sri Lanka) the following year.