June 17 (UPI) -- Britain's royal family took part in a parade through London on Saturday to mark Queen Elizabeth II's 91st birthday.
"This military ceremony dates back to the early eighteenth century or earlier, when the colours (flags) of the battalion were carried ('trooped') down the ranks," the family's official Instagram account said in a message captioning a photo of the monarch with Prince Philip, her husband of 70 years. "From the reign of Edward VII onwards, the Sovereign has taken the salute in person at Trooping the Colour. During her reign, The Queen has attended Trooping the Colour every year except 1955 when it was cancelled because of the National Rail Strike."
Elizabeth has been queen since 1952.
After the British Army's military display for the Horse Guards Parade on Saturday, the monarch joined family members -- including her son Prince Charles, Charles' son Prince William, William's wife Kate Middleton and their children George and Charlotte -- on the balcony of Buckingham Palace to watch the Royal Air Force Red Arrows display.
Elizabeth began the day by observing a moment of silence for the victims of this week's fire at Grenfell Tower before the event. At least 30 people were killed in the London apartment building blaze, with many more still missing.