Part of a weekend of commemorations to mark her 90th birthday, the monarch was greeted with a royal salute, before carrying out an inspection of the troops.
The Trooping of the Colour parade is a traditional military ceremony that dates all the way back to the 18th century.
Grandson Prince William, his father Prince Charles and aunt Princess Anne rode horses during the parade, a tradition that originates from preparations for battle, when flags are carried or “trooped” down the rank for soldiers to see.
Among them was Britain’s Got Talent victor and Household Cavalry bandsman Richard Jones whose skill as a magician saw him triumph in the popular show.
On Sunday, a giant street party known as the Patron’s Lunch will be held on The Mall outside Buckingham Palace to mark the queen’s official birthday.
Britain’s Queen Elizabeth II and the Duke of Edinburgh leave Buckingham Palace in central London to view the Trooping the Colour ceremony at Horse Guards Parade as the Queen celebrates her official birthday, Saturday Jun.
The little princess appeared calm throughout the event and was seen coolly watching the flight of Red Arrows show roaring through the sky in flawless formation while occasionally breaking into a lovely smile and wave to the crowds.
Ala Lloyd, who is the creative director of the carnival parade, told the BBC the eras of the Queen’s reign through the decades are being symbolised by different sections of the parade.
Standing for hours in the heat, which reached about 21 degrees, and dressed in a full military uniform, took its toll on the guard. He performed magic tricks for his captors but used their food so he could supplement his meagre diet.
Camilla, Duchess of Cornwall, and Catherine, Duchess of Cambridge, travel in a carriage to take part in Saturday’s festivities honouring the Queen.
A soldier faints performing the colour of trooping for the Queen Elizabeth’s birthday.
“Think of all the rehearsing and the square bashing”.
The royal couple lead the family onto the palace balcony waving as the Royal Air Force jets and vintage World War II planes fly overhead.
“There will be lots of colour, lots of noise, lots of movement and it’s going to be hopefully a fantastic day”.
“We’ve got to get in over 160 vehicles overnight tonight to be able to put out all the tables and make sure everything’s ready for when the doors open tomorrow morning”.