'Entirely the Wrong Way’: Queen Elizabeth II Broke Royal Protocol at William and Kate’s 2011 Wedding

British royal protocol is ancient and complex, and faux pas' can even occur with reigning sovereigns, as the late Queen Elizabeth II discovered when arriving at Prince William and Kate Middleton's 2011 wedding.

"I spotted that the car conveying the queen and the Duke of Edinburgh pulled up entirely the wrong way in Dean's Yard at Westminster Abbey," protocol expert Alexandra Messervy dished on an upcoming installment of "A Right Royal" podcast.

"The queen got out on the wrong side and there was a bit of a fluster," she added. "I think the [guard] who opened the door appeared flustered when the queen was actually not where she would normally be. The correct protocol for her was to be on the curbside, and she was on the reverse side."

Messervy continued: "It is correct for the female to get out on the curbside. It's all because of the days of carriages and horses. The gentlemen enjoyed the outside of the pavement while the women were on the other to avoid the mud."

Even though Elizabeth II could have accidentally forgotten the protocol, the expert explained that Her Majesty may have had "a sore leg that day and she couldn't let herself out on the left."

Kate has officially been a senior member of the British royal family since marrying Prince William in 2011. As the Duchess of Cambridge and now the Princess of Wales and future Queen Consort, the princess has overcome the odds of marrying into the monarchy.

Royal brides such as Princess Diana, Sarah Ferguson, and eventually Meghan Markle were not able to stay the course, but Kate has thrived in her role and is now calling the shots in the family. But according to a source, the wife of the heir to the throne had to learn her royal role on her own.

Kate first met William when they were students at St Andrews University in Scotland back in 2001. The two teenagers took their relationship slow, and it was a full decade after they met, including a brief breakup in 2007, before the commoner officially became a princess at their lavish Westminster Abbey wedding.

During the reign of Queen Elizabeth II, informality was not stressed in the royal family and working senior royals were expected to learn how to behave and display protocol as they went along. Diana once spoke about how hard it was when she joined the monarchy in 1981 since she had very little guidance on how to be a princess.

Even one of Britain's "greatest-ever monarchs" showed that when it comes to just how much protocol there is to remember, those who steer the royal ship make mistakes as well.

Us Weekly reported on Messervy's remarks.