While it is not an official rule, it is often considered a practical and respectful choice that senior royals pack a black outfit when traveling internationally. Packing a black dress or suit became a part of customary protocol by senior royals when traveling, and started in the 1950s, due to a rather tragic reason. It was in 1952, that Princess Elizabeth II was on tour in Kenya with Prince Philip when she got word that her father, King George VI, had died due to a long standing illness. Unfortunately, because she had not packed a black dress, upon her abrupt return to the UK, she couldn’t leave the plane until a member of her staff had delivered a black dress for her to wear off of the flight. Ever since that fateful trip, a black ensemble has been known to be a staple packed by royal aids to-date.
The black outfit serves as a contingency plan in case a member of the royal family needs to attend a funeral or a period of mourning arises while they are abroad. As representatives of the United Kingdom, it is essential for the senior royals to be prepared for such occasions and show appropriate respect and solidarity. This practice ensures that they are prepared to fulfill their roles and responsibilities as representatives of the monarchy, regardless of the circumstances they may encounter during their travels.
Why black you may ask? Black is a traditional color associated with mourning in many cultures, and by having a black outfit readily available, senior royals can avoid any potential issues of not having suitable attire in case of an unexpected event. In fact, it is deemed good etiquette and a matter of protocol in many countries and cultures when mourning to wear black.
While we wish them never to have to use such an item, it does remain the one thing you can always count on being packed during international travel for senior royals.