During his visit to Kinneil House, King Charles was observed wearing the customary Scottish attire.
This deviates from a tradition followed by male members of the royal family, as his eldest son, Prince William, has yet to be seen in the tartan.
Despite the royal family's close connection with Scotland, where they spend several months each year at Balmoral Castle, it is customary for royal men to wear kilts while in Scotland.
King Charles was photographed wearing a kilt on multiple occasions during the celebration that formally acknowledged him as the monarch at Kinneil House, following the example set by his father, Prince Philip.
However, Prince William and his younger brother, Prince Harry, have not been seen wearing kilts since reaching adulthood. Prince William himself has strong ties to Scotland, having attended St Andrew's University, where he met his wife Kate Middleton.
At his graduation ceremony, Prince William chose to wear a black suit, a white bow tie, and a graduation gown, rather than a kilt.
The reasons behind the prince's decision to not wear a kilt have never been disclosed, raising concerns that the tradition might fade away when he becomes the monarch after his father.
The Stewart Royal tartan, which is closely associated with the family, traces its roots back to the House of Stewart.
However, a retailer seeking permission to sell this tartan received a response from the royal household stating that the tartan adopted by the King and the royal family is strictly personal and private.
It was explicitly emphasized that the tartan cannot be worn by others, purchased from any source, or manufactured for general sale.