Queen Elizabeth II's birthday party a royal tradition

Last Updated Jun 13, 2015 6:30 PM EDT

Queen Elizabeth II turned 89 on April 21, but her official birthday celebration was Saturday. Crowds gathered at Buckingham Palace in tribute to her majesty the queen and to see generations of the royal family.

"Trooping the Color," as Saturday's celebration was called, is a centuries-old throwback, carrying or "trooping" the colors of regiments on the battlefield, CBS News' Charlie D'Agata reports.

Looking remarkably well-rested for the mother of a newborn, Kate led the way along with Prince Harry and Camilla in the lead carriage. Beneath a bearskin hat was husband Prince Phillip, who just turned 94 years old this week. Pulling up on the rear in horseback was Prince William alongside Prince Charles.

For the 1,400 members of the queen's own troops, this display of military pageantry is one role taken very seriously, royal correspondent Roya Nikkhah said.

"There is no bigger occasion than 'Trooping the Color' for anyone who is a member of the household division, or the household cavalry," Nikkhah said. "It's the pinnacle of what they do. It takes six months to prepare a solider and a horse to go on parade, and it takes up to two days to perfect and polish all the kits that go on display."

And with meticulous attention to detail. Nobody wants to spoil the head of the armed forces' big day.

The queen's actual birthday was back in April, but the official sovereign's birthday parade has been a tradition since 1748.

The queen's great-grandfather, King Edward VII, decided June had better weather than his birthday in November.

But whatever's to be said about mad dogs and Englishmen, over the years the odd soldier has succumbed to the midday sun.

For most of her reign, the queen used to be at the reins, inspecting the troops on horseback until 1986.

Although her mount flinched in 1981, when a man fired six blanks at the queen, she kept her cool and kept the horse under control.

She is said to relish sharing the celebration with her subjects, especially as she nears the moment this September when she becomes Britain's longest-reigning monarch.

"'Trooping the Color' is now quite a poignant event for the public," Nikkhah said. "When they look at the queen and think, my God, she's about to make history in this country, I think it's a very special occasion for the public and the royal family to mark that."

The whole point of the exercise is to inspect the troops, but what's really on show is the entire royal family.