The large piece of graffiti – stylised “tags” along with symbols including a star, a heart and the word “king” – was sprayed on the front of an upper section of the elegant 19th century structure that looks out onto Milan Cathedral and Piazza del Duomo.

Three youths, dressed in black, were filmed as they performed the act of vandalism at about 10pm Monday night, as onlookers below jeered and whistled at them.

Firefighters lit up the structure to help police catch the culprits but the three managed to escape over rooftops.

The vandalism has been condemned by politicians of all colours.

ANSA