Eventually, the two rows were separated, with the longer one being put into the joyas de pasar (jewellery to be passed down) collection.
It is believed the tradition of adding diamonds to the collet stops with Queen Letizia.
As for when she was last seen wearing the diamond necklace, the royal stepped out with it last November.
She hosted an official state dinner at the Royal Palace of Madrid with Italy’s President Sergio Mattarella as the guest of honour.
The royal wore a black floor length gown for the occasion and also wore the Queen Maria Christina’s Loop Tiara.