Prince William and Catherine, Princess of Wales — widely known as Kate Middleton — have made a subtle but notable adjustment to how they are styled publicly, in line with long-standing royal tradition.

The change came during a recent official visit to Scotland, where the couple were referred to by the regional Scottish titles Duke and Duchess of Rothesay instead of their more familiar “Prince and Princess of Wales.” This shift reflects a centuries-old custom in which members of the British royal family use different titles depending on where they are in the United Kingdom.

In Scotland, the title “Rothesay” has been traditionally held by the heir to the Scottish throne since the 14th century, long before the formation of the United Kingdom. As such, when William and Kate represent the monarchy north of the English border, they do so under these historic regional titles.

Both William and Catherine already hold a range of other titles — including Duke and Duchess of Cornwall and Earl and Countess of Chester — through their positions as heir and heir-apparent’s spouse following King Charles III’s accession to the throne in 2022.

The decision to be styled as the Duke and Duchess of Rothesay during Scottish engagements is not new, but it has drawn attention because few members of the public fully understand the tradition. Royal experts say it underscores the couple’s growing role as senior representatives of the monarchy and highlights how Britain’s royal titles have evolved.

Observers also note that this kind of subtle title change usually goes unnoticed unless the couple is on official duties in regions where alternate styles are customary. Despite the shift, William and Catherine remain most widely known around the world as the Prince and Princess of Wales.

As Prince of Wales, William is first in line to succeed King Charles III, and Catherine is expected to become queen consort when that occurs — at which point her official style would change once again.

For now, though, the duchies and titles they choose to use are rooted in tradition, geography, and centuries of royal history — even if they fly under the radar for most people.