European royalty is entering uncharted waters - the more so as widespread legal changes mean that in the majority of countries, girls are now entitled to inherit the crown.
Proud parents Queen Letizia and King Felipe were also in attendance at the Royal Palace in Madrid as the 18-year-old heiress presumptive marked the start of the new year in full military dress.
The teenage heir to the Spanish throne swore an oath to the constitution on her 18th birthday, and looks set for a more high profile role in 2024, beginning with the Pascua Militar ceremony tomorrow.