LONDON -- Queen Elizabeth II and her husband Prince Philip have attended a ceremony honoring her birthday.

The parade of horses, soldiers and musicians called "Trooping the Color" is the first official event attended by Philip since he left the hospital last week, following treatment for a bladder infection.

The royal couple rode in a vintage horse-drawn carriage for the parade in central London, where thousands of people turned out to watch the military spectacle.

"Trooping the Color" is an annual ceremony marking the queen's official birthday, which takes place in June. The monarch's actual birthday was on 21 April, when she turned 86.

The ceremony originates from traditional battle preparations, when "colors", which refer to military flags, were carried down the rank to be seen by soldiers.

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  • LONDON, ENGLAND - JUNE 16: Prince Philip, Duke of Edinburgh, stands on the balcony of Buckingham after the Trooping the Colour ceremony after the Horse Guards Parade on June 16, 2012 in London, England. (Photo by Dan Kitwood/Getty Images)

  • Britain's Queen Elizabeth II and Prince Philip, center, watch a Royal Air Force fly pass with their family from the balcony of Buckingham Palace after the Trooping The Colour at the Horse Guards Parade in London, Saturday, June 16, 2012. (AP Photo/Sang Tan)

  • Queen Elizabeth II and Prince Philip watch soldiers ride past Buckingham Palace following the Queen's Birthday Parade, 'Trooping the Colour' at Horse Guards Parade in London on June 16, 2012. (LEON NEAL/AFP/GettyImages)

  • Left to right, Queen Elizabeth II, Prince Philip, Duke of Edinburgh, Lady Louise Windsor and Catherine, Duchess of Cambridge arrive on the balcony of Buckingham Palace after the Trooping the Colour ceremony and the Horse Guards Parade on June 16, 2012 in London, England. (Photo by Dan Kitwood/Getty Images)

  • Prince Philip, left, Prince Harry, second left, Catherine, Duchess of Cambridge, second right, and William, Duke of Cambridge, right, stand on Buckingham Palace balcony following the Queen's Birthday Parade, 'Trooping the Colour' at Horse Guards Parade in London on June 16, 2012. (LEON NEAL/AFP/GettyImages)