At the annual Trooping the Colour, royal family fans was able to get a closer look at the next generation of royals, specifically Prince William and Kate Middleton’s children. There was Prince Louis, who looked cute and adorable at his first public appearance.

Older brother Prince George, the child who would one day wear the crown after his father, was in attendance as well. Princess Charlotte, William and Kate’s only daughter, was also present, which started speculations as to the kind of tiara she might be wearing one day.

But according to a jewelry expert, it might not happen anytime soon. Based on tradition, women can only wear a tiara if they are the bride or are already married. “The tiara has its roots in classical antiquity and was seen as an emblem of the loss of innocence to the crowning of love,” explained Geoffrey Munn, a London-based jewelry expert.

However, an expert on royal etiquette explained that there is actually an exception to this tradition, which might allow Princess Charlotte to wear a tiara even if she’s not yet married. “Single ladies don't typically wear tiaras unless they are born into the Royal Family as a princess,” Grant Harrold, a former royal butler, said.

This means that the young princess can opt to follow tradition and wait until her wedding day to wear a tiara. There are a number of female royals, such as Princess Eugenie, Kate Middleton and Meghan Markle, who chose this route and only wore their tiaras on their wedding day.

On the other hand, Charlotte, as a princess, might also choose to ditch tradition and wear a tiara before she gets married following the footsteps of some of her older relatives. For instance, Queen Elizabeth II’s younger sister, Princess Margaret, has been known to wear a tiara all her life even before her marriage to Antony Armstrong-Jones. Princess Anne was also seen wearing a tiara a couple of times before she married Mark Phillips.

But royal family etiquette can be pretty strict when it comes to wearing tiaras. Just because one is a princess it would mean that she can wear a tiara any time of the day.

“Tradition dictates that tiaras are not worn before 6 p.m., though weddings are an exception,” commentator Richard Fitzwilliams told Insider. “They are worn on formal white tie events and state occasions such as state banquets. The decision on whether to wear a tiara is linked to the dress code of a particular event and also to personal preference.”

Kate wears a tiara sparingly and only at white tie events. In fact, observers have noted that the Duchess of Cambridge has only worn a tiara only nine times, the last one was during the state banquet hosted by Queen Elizabeth for Donald Trump.

Princess Charlotte and Prince George Princess Charlotte of Cambridge and Prince George of Cambridge attend the wedding of Princess Eugenie of York to Jack Brooksbank at St. George's Chapel on Oct. 12, 2018, in Windsor, England. Victoria Jones - WPA Pool/Getty Images