Kate Middleton Baby Bump, Due Date [PHOTOS]: Pregnant Duchess' Final Public Appearance Before July Birth, 'Trooping the Colour' Parade

Prince William's wife made her final solo appearance earlier this week when she christened the new Royal Princess cruise ship, but today was her final general public appearance at the "Trooping the Colour" celebration. The Duchess of Cambridge was joined by her in-laws the Duke and Duchess of Cornwall, her brother-in-law Prince Harry and of course her husband William. Together, the royal family celebrated the 87^th birthday of Queen Elizabeth II (her actual birthday is April 21).  The Queen's husband, Prince Philip, was not present as he still remains in the hospital, recovering from exploratory abdominal surgery.

Prince Harry and Camilla, Duchess of Cornwall, accompanied the 31-year-old mother-to-be in a horse-drawn carriage at this televised military ceremony, which is held every year during the Horse Guards Parade in London's Whitehall. Kate, who is eight months pregnant, wore a pale pink Alexander McQueen coat with a matching hat and waved to the spectators, smiling all the way.

Kate Middleton's husband, Prince William, took part in the event riding on horseback.

The Queen might not have been accompanied by her husband (who has now missed a total of three "Trooping the Colour" parades - the two other instances were due to royal duties), she invited her cousin, the Duke of Kent, to accompany her in her glass coach for the short trek from Buckingham Palace along The Mall. This glass coach is used in numerous events such as royal weddings, including the Queen's own wedding to her husband in 1947 when she was still Princess Elizabeth.

The "Trooping the Colour" parade originated from traditional battle preparations, when "colours" (military flags) were carried down the rank to be seen by soldiers. Queen Elizabeth II took the royal salute as members of the royal family looked on.

This traditional ceremony is also an important social occasion for the participating Guardsmen. Plus, "Trooping the Colour" gives their wives, girlfriends, and relatives the chance to celebrate the achievements of these men and also to see the royal family.