The Trooping of the Colour parade takes place every year to mark the monarch’s official birthday. Queen Elizabeth II celebrated her 95th birthday back in April, but a British monarch’s official birthday always happens in June.
The brooch’s central aquamarine is bright blue and rectangular.
It also features other smaller aquamarines, as well as diamonds.
According to the Court Jeweller, the brooch’s unique shape and design suggests that it may be able to be separated and worn as a pair of clips.
The brooch dates back to at least the 1930s and one of its first appearances was in 1939, when the Queen Mother wore the jewel to meet with President Lebrun of France at Windsor Castle.
The brooch was given to Queen Elizabeth II when her mother died in 2002, but it was kept in a jewellery box for more than a decade.
Her Majesty’s first public appearance wearing the brooch was in June 2014, when the monarch donned the jewel for the Royal Ascot.
At the time, the monarch matched the brooch with a pale blue outfit, complete with a ribboned straw hat and her iconic pearl necklaces.
Today, Her Majesty was wearing her three strings of pearls, as well as a grey hat to match her coat dress.
The coat dress featured lemon-coloured flowers around the neckline and buttons down the front.
It was created by British fashion designer Angela Kelly, who has served as Senior Dresser to the Queen since 2002.
To complete her outfit, the Queen wore white gloves and carried a black and gold handbag.
The monarch’s shoes were her black and gold loafers, which are slightly heeled.
Today’s Trooping of the Colour was Britain’s longest-serving monarch’s 69th parade.
Although slightly smaller due to the coronavirus pandemic, the birthday parade was still a splendid display, with the RAF’s red arrows flying past Windsor Castle to mark the end of the 45-minute-long event.