He was a cultured man, who expanded significantly the library started by his ancestor Íñigo López de Mendoza, 1st Marquis of Santillana [REF].
In 1560 the duke entertained widower King Philip II of Spain while traveling to collect one of his wives, the 17-year-old French Princess Elizabeth of Valois, (1543-1568), first promised to one of Philip's sons, Carlos, Prince of Asturias.