King Felipe of Spain, following a tradition dating back to the XVII century, took possession of the title of Protocanon of the Liberian Chapter of Santa Maria Maggiore, one of the four major papal basilicas in Rome.
The title was confirmed by the 1953 Concordat between Spain and the Holy See. Before him, Alfonso XIII was installed in 1923 and King Juan Carlos in 1977.
Other papal basilicas have links to other European countries. The President of France is Protocanon of San Giovanni in Laterano and the King of the UK has been recently istalled as Royal Confrater of St. Paul outside the walls.

Some info in English

https://www.basilicasantamariamaggiore.va/en/eventi-e-novita/2026/presa-di-possesso-del-titolo-di-protocanonico-del-capitolo-liber.html

Info from Casal Real, in Spain, with pictures and video.

https://www.casareal.es/ES/Actividades/Paginas/actividades_actividades_detalle.aspx?data=16879