STORY: Also known as the Queen's Birthday Parade, "Trooping the Colour" has more than 1,200 soldiers taking part along with military bands. It has been held for more than 260 years.
It comes on the first of four days of celebrations in Britain to mark Queen Elizabeth's seven decades on the throne.
The queen has attended every such parade bar one since 1955, with scaled-down ceremonies taking place in the last two years because of coronavirus restrictions. Due to her mobility issues, for the first time she will take the salute from soldiers and officers from the balcony of Buckingham Palace.