Lucia was the daughter of the former Chilean ambassador to London, and reportedly told Charles she had "just the girl" for him before hooking him up with Camilla.
The pair were said to have bonded over their love of polo and being outdoors.
Camilla reportedly made a joke about her great-grandmother Alice Keppel having an affair with King Edward VIII, saying, "My great-grandmother was the mistress of your great-great-grandfather. I feel we have something in common."