The wardrobe selections made by Kate Middleton and other members of the royal family are highly scrutinized for both fashion and propriety. Between hats, tiaras, and vibrantly colored outfits for the women, and rather glamorously adorned military ensembles for the men, the British royal family almost always stands out in a crowd. But there’s a time and place to just wear black, and it’s after the death of a relative.

In case a relative passes away while family members are traveling, every person must pack a single, all-black outfit, The Independent reports. This guarantees that they’ll be dressed respectfully when seen in public after the announcement.

The sensible policy arose after a real-life snafu in 1952, which fans of Netflix’s The Crown may recall having been depicted during the first season of the series. Then-Princess Elizabeth had been visiting Kenya with her husband Prince Philip when her father, King George VI, passed away from lung cancer. The young couple promptly returned to England, but Elizabeth didn’t have any appropriately somber clothing in her suitcase. She stayed on the airplane until somebody brought her a black outfit.

The Independent explains that newscasters must also travel with a black outfit, in case they have to report on the death of a royal family member while abroad.

The all-black rule is one of many other fashion regulations that govern the royals. Some are equally practical, like wearing gloves to prevent the spread of germs or weighing down hemlines with tiny lead curtain weights to prevent Marilyn Monroe moments. Others, like subtle nail polish colors and pantyhose, center on decorum. And sometimes, the queen’s handbag is actually sending a secret signal to her staff.

[h/t The Independent]