A 500-year-old secret code used in letters between one of Spain's most famous monarchs and a military commander has been cracked.
Ferdinand of Aragon's letters have tantalised historians for centuries.
Constructed using more than 200 special characters, they were deciphered by the country's intelligence agency.
He was behind the final recapture - Reconquista - of Spain from the Moors in 1492 and Columbus's journeys to the Americas.
The letters between Ferdinand and Gonzalo de Córdoba include instructions on strategy during military campaigns in Italy in the early 16th Century. They were written using secret code in case they fell into enemy hands.