The Duke and Duchess of Cambridge will never set out upon a royal tour without this one thing.
No, itโs not a macaroni necklace made by Princess Charlotte, or even a pair of uggs for the flight home, but rather an entirely black outfit only to be worn in the very unfortunate case that a family member may die in their absence.
And itโs not a custom exclusive to just Wills and Kate.
In fact, reports reveal the entirety of the British Royal Family must be prepared.

The Duke and Duchess will never travel without a mourning outfit prepared.
When Princess Dianaโs father Lord Spencer sadly passed away while she and Prince Charles were on a skiing trip through the Alps in 1992, the couple were ready with an all-black ensemble for the journey home.
Perhaps the ruling came after Queen Elizabeth IIโs father George VIโs death in 1952. When she and Prince Philip were participating in a Kenyan safari, photographers were unable to capture the pair until mourning outfits were brought in for them to wear.
Fans will recall this as a true moment harrowingly told in season one of The Crown.

Queen Elizabeth and Prince Philip return from Kenya following the death of King George VI.
Itโs not the only fascinating royal rule in place โ thereโs a myriad of intriguing protocol in place that the British family must follow at all times.
Until recent years, direct heirs used to be forbidden to travel together. Before the aviation industry evolved, direct heirs were never put in the same plane together in case it went down for fear of losing two potential rulers in one hit.
While quite a morbid strategy, these days the rule has been relaxed and youโll often see Prince William and Prince George jetting about in the same aircraft.

Rules have relaxed, and Prince George and Prince William are able to fly together.
And youโll never catch a royal accepting refreshments during a walk-about tour, no matter how peckish they may be.
Itโs not because he doesnโt have a sweet tooth, itโs simply because itโs too much of a security risk to accept food from strangers. So donโt be offended if your treat gets tossed, the decision to simply not eat it is a big step up from the way the royal family used to handle the threat โ employing โfood tastersโ to test their meals for poison.
WATCH the video for more of Duchess Catherineโs most fashion-forward looks to date!