Prince Harry and Meghan Markle
Prince Harry and Meghan Markle's guests have to follow some rules when they meet Queen Elizabeth II. Pictured: Prince Harry and Markle arrive to attend a memorial service at St Martin-in-the-Fields in Trafalgar Square in London, on April 23, 2018. Getty Images/Victoria Jones

Prince Harry and Meghan Markle's wedding guests will need to follow some rules during the event, especially when they meet Queen Elizabeth II.

To ensure that the royal wedding will be in order, Prince Harry and Markle reportedly sent their guests seven pages of "critical guidance." The list also includes the do's and dont's they need to remember when they meet the queen.

According to Express, the guests have to curtsy to the monarch and should address her as "Your Majesty" and not "Your Royal Highness." A number have made mistakes in addressing the Queen properly. However, one should not be alarmed as this is not equivalent to breaking the law.

"There are no official legal rules in place," said Lucy Hume, associate director at professional etiquette coaching company Debrett's. "Apologise if you feel you may have caused offence, but try not to panic, and stay calm."

"It would seem from what we've seen of members of the royal family in public that they are very accustomed to a variety of different situations," Hume continued. "They meet people from different backgrounds all the time and they're very accustomed to putting people at ease; it’s unlikely you would cause offence."

Royals are accustomed to meeting different people and being subjected to different scenarios. However, when one wants to take a selfie with the Queen, she advised asking for permission first to show respect to the Queen's boundaries.

"It's not usually appropriate to do so," Hume said about taking a selfie with Her Majesty. "So if you do want to take a photograph, ask their permission first, possibly get somebody else to take a photograph but it’s important to respect that person’s personal space."

Aside from the rules mentioned, the guests are not allowed to take photos during the ceremony. "All guests will be asked to surrender mobile telephones… and any devices used for image capture," the guideline read.

There is also a scheduled time when guests are allowed to use the bathroom. "Guests are advised that there are very limited toilet facilities in St George’s Chapel, but these are available for guests’ use between 9am and 11am at which point this facility will become restricted for the duration of the service," the note added.

Prince Harry and Markle are tying the knot on May 19 at St. George's Chapel at Windsor Castle.