Queen Elizabeth was in another country when she learned she was going to be the next ruling monarch of the UK and her father had died, but because she wasn’t prepared for the news and had to delay her return to her home country, the monarch now makes sure to have one specific item with her whenever she travels.

According to the documentary “Secrets of the Royal Flight,” the Queen was unable to return to the UK following her father’s death because didn’t have special mourning outfits on hand while on a six-day tour in Kenya and had to wait for some to be brought to her so she could exit the plane once back on English soil.

“At the time, her luggage and clothing was for a royal tour of Africa so she wasn’t suitably attired to leave the aircraft,” the documentary reveals. “Special mourning outfits were brought to the aircraft for her to wear before she came down the steps for the press and the media to see her clearly very upset.”

As a result of her not being prepared for her father’s death, a new rule was added to royal protocol as a result, requiring that when members of the royal family traveled abroad, they must always have an all-black ensemble packed and at the ready to avoid any similar issues. To date, the rule is followed by all members of the family, including the now 93-year-old Queen herself.

“This extraordinary milestone in royal history would change protocol for the family forever,” the documentary states. “The Queen currently travels with at least three outfit changes a day but an all-black ensemble for the purposes of mourning is always included too just in case.”

While the all-black ensemble while traveling is a required royal protocol, there are other reported rules members of the royal family, especially women, have to follow, though they are more preferences of the Queen herself.

One such rule regards the amount of makeup female members of the royal family can wear on their faces, and it’s preferred they do not use an exaggerated amount.

Queen Elizabeth II
Queen Elizabeth II is seen at the Chichester Theatre while visiting West Sussex on Nov. 30, 2017, in Chichester, United Kingdom. Getty Images/Stuart C. Wilson