After the ceremony the royal family will head back to Buckingham Palace and gather on the balcony to watch the RAF flypast. She smiled - both at the jets and the children.
Meghan has become particularly close to her father-in-law, who walked her down the aisle and was instrumental in helping Meghan and Harry with wedding planning.
But Peter and Autumn Phillips' seven-year-old daughter Savannah, who was with her sister Isla, could be seen playing up as everyone stood still while the national anthem was played.
In the 18th century, guards from the royal palaces assembled daily on Horse Guards to "troop the colours" and in 1748 it was announced that the parade would also mark the Sovereign's official birthday. "I hope that more people like me, not just Sikhs but from other religions and different backgrounds, that they will be encouraged to join the Army".
Trooping the Colour originated from traditional preparations for battle.
Tens of thousands of Royal fans flocked to Buckingham Palace and the Mall to catch a glimpse of the pomp and pageantry surrounding the celebration for Queen Elizabeth.More news: A Championship Contender May Have Just Entered The Race For Kawhi Leonard
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The Duke and Duchess' attendance of the 2017 games in Toronto, Canada, where the couple watched the wheelchair tennis, was their first public appearance.
And unlike her new royal counterparts, the Duchess of Sussex's pale pink design featured short sleeves, with a Philip Treacy hat, as she beamed with joy on a gloriously sunny Saturday in central London. Prince Harry sported military attire, as did his brother, Prince William, and father, Prince Charles.
Queen Elizabeth II also selected a blue ensemble, choosing a dress and hat in a bolder blue than the shade chosen by Middleton and Parker-Bowles.
Prince Philip, the Duke of Edinburgh, did not take part today, in line with his retirement from public life previous year.
Some 7,500 guests joined the monarch at Horse Guards, with prime seats accorded to U.S. Defense Secretary James Mattis and Britain's Defense Secretary, Gavin Williamson.