LONDON (CNN) -- A grieving nation began its final farewell to Diana, the Princess of Wales, Saturday as the cortege bearing her coffin made its solemn, measured trip through packed London streets.

People hugged one another and gazed in tearful silence as the coffin, draped in the maroon, yellow and blue Royal Standard, was escorted by soldiers through the streets on a gun carriage drawn by six horses.

On top of Diana's coffin lay three wreaths of white flowers, one each from her brother, Earl Spencer, and from her sons, Prince William, 15, and Prince Harry, 12.

Despite the throngs, the predominant sounds were those of the horse hooves striking the pavement and of Westminster Abbey's Tenor bell tolling, once each minute.

Some people held the British flag. A few tossed flowers and some held lit candles in the bright morning sunlight.

The 3 1/2-mile processional route began at Kensington Palace, Diana's London home at the west end of Hyde Park, and wound through major streets en route to Westminster Abbey.

Hundreds of thousands of people filled London's streets to say goodbye to the popular princess, and huge television screens were set up in Hyde Park and Regent's Park to try to ease the anticipated crush.

The route included many of the capital's primary landmarks, including the official royal residence of Buckingham Palace, the Prince of Wales home of St. James's Palace, the prime minister's home at Downing Street and Parliament.

Members of the royal family stood together outside as the cortege passed Buckingham Palace.

Prince Charles, Prince William, Prince Harry, Diana's brother Earl Spencer and Queen Elizabeth's husband, Prince Philip, joined the march for the final mile. The boys walked behind their mother's coffin with heads bowed, flanked on either side by their father, uncle and grandfather.

Representatives of a number of Diana's favorite charities, some of them in wheelchairs, also joined the procession.

The day's events were spelled out in detail. During the two-hour procession, guests arrived at Westminster Abbey for admission, in scheduled sequence, for the 11 a.m. funeral.

Members of the royal and Spencer families were the last to be escorted into the church, arriving at the Abbey shortly before the coffin.

In a break with precedence, the Royal Standard was lowered and replaced by Britain's flag at half-staff at Buckingham Palace.

Buckingham Palace and the Spencers invited 2,000 people to the service. To accommodate them all, some were to be ushered into St. Margaret's Church, next door to the Abbey, where they would be able to watch on a video link.

Among those in attendance were entertainers including Sting, Tom Hanks, Luciano Pavarotti, Diana Ross, Tom Cruise and his wife Nicole Kidman, and director Steven Spielberg. Elton John, who was to sing a refashioned song for the service, walked into the abbey alone.

Dignitaries included British Prime Minister Tony Blair, U.S. first lady Hillary Rodham Clinton and former British Prime Minister Margaret Thatcher.

Also in attendance were Mohamed Al Fayed and his wife, the parents of Dodi Fayed, Diana's new love who was killed with her in the car crash in Paris last weekend.

The funeral was "a chance to show to the whole world the British nation united in grief and respect," the queen said Friday in a rare public address.

"May those who died rest in peace and may we, each and every one of us, thank God for someone who made many, many people happy."

Tens of thousands of mourners signed condolence books at St. James's Palace through the week. Those were closed Friday, but were to be reopened Saturday afternoon at Kensington Palace.

The coffin containing the body of the princess was brought Friday evening from St. James's, where it was kept privately in the Chapel Royal, to Kensington Palace.