Letter from Holy Roman Emperor written in secret code finally cracked after 5 centuries to reveal he was worried about being assassinated

• The letter written by the Holy Roman Emperor Charles V has been deciphered.

• The secret of the 16th century was revealed in a three page letter.

• The French scientists took months to decode the letter.

The letter was signed by the Holy Roman Emperor Charles V and was deciphered by French scientists.

During an era of religious and strategic conflict, the most powerful man in Europe wrote a secret letter. It showed that Charles V prioritized his relationship with King Franois I of France over his own safety.

The royal secrets of the 16th century are revealed in a three-page letter written in plain script and some in a mysterious code.

The letter had been in the library for almost 500 years. Cecile Pierrot heard a rumor at a dinner party and went to the library's basement to look for it.

Spain, southern Italy, the Netherlands, and swathes of central Europe were all ruled by Charles V.

Against the backdrop of continental wars and religious conflict between Catholics and Protestants, it was necessary for the emperor to communicate secretly and not give away any information to the public.

The contents of the letter have been a mystery since it was composed of about 120 symbols and passages.

Pierrot gave all the symbols a name and put them into a programming language, but it couldn't open the mystery language.

Pierrot and her team set to work for months wading through the strange script invented by Emperor Charles to identify decoy letters and get slow and steady eureka moments.

The themes identified by the team have given an insight into the thinking of a giant figure at a turning point in Europe's history.

Business Insider has an article on it.