French scientists don decode one coded 500-year-old letter wey di most powerful ruler for Europe write and sign for year 1547.

For di letter, di Holy Roman Emperor Charles V reveal say im dey live in fear of assassination attempt by one Italian mercenary.

Di emperor bin send di letter to im ambassador for di French royal court – di man wey im name na Jean de Saint-Mauris.

Di letter bin give insight into di concerns of Europe rulers for di time of dangerous instability wey wars of religion and rival strategic interests cause.

For historians, dis also na rare glimpse of di dark arts of diplomacy in action: secrecy, fake smile and disinformation wey dey for dat time and still dey exist today.

How scientists take decode di letter

Cryptographer Cecile Pierrot bin first hear rumour of di existence of di letter for one dinner party for Nancy three years ago. After lengthy research, she track am down to di basement of di city historic library.

She challenge herself to decode di document within a few days but she later realise say di work hard pass wetin she tink.

Di three-page letter – get about 70 lines – dem use about 120 encrypted symbols write am but three sections also dey wey be say na plain contemporary French dem take write am.

"Di first thing na to categorise di symbols, and to find patterns. But dis one no be simple case of one symbol dey represent one letter – e hard pass am," Pierrot tok.

"To just put am inside computer and tell di computer to work am out go take longer time pass di history of di universe!"

Little by little she and her team begin make progress. She see two types of symbol: simple and complex. Dem no write di vowels as letters, but dem add am as diacritical marks as in Arabic. Di 'e' vowel no dey.

Dem also discover say while most symbols represent letters or combinations of letters, odas represent whole words - like needle for English King Henry VIII. And some symbols dey wey no get any function at all for di letter.

Finally di breakthrough come wen historian Camille Desenclos point di team to oda coded letters wey di emperor don send and receive. For inside one of dis letters dem hide for Besançon, di receiver don make informal translation.

So wetin dey di letter?

Di team neva issue full translation. Dem dey save am to publish for one academic paper. But dem don arrange di themes.

February 1547 na period wey peace no too dey between di rival powers of France and di Holy Roman Empire.

Emperor Charles V – na ruler of vast areas wey include Spain, di Netherlands, Austro-Hungary and southern Italy – e no longer actually dey at war wit King Francois I. But dem still no trust themselves.

Two recent events bin dey di two rulers minds. Di first na di death of Henry VIII wey die just a few weeks before. And di second na di rebellion for Germany wey one Protestant alliance dem call di Schmalkaldic League dey cause.

For di letter, Charles V reveal im concern to maintain peace wit France so dat im go fit focus im forces against di League.

E tell di ambassador to keep imself up-to-date of wetin dey happun for di French court, in particular any reaction to di death of King Henry.

Wetin im wan avoid pass na make di French and English no collabo to support di Protestant rebels.

Pierre Strozzi. Saint-Mauris wan find out if dis tori na just gossip, or genuine threat?

And finally, di longest part of di letter Charles V set out for im ambassador na di current state of play for im campaign against di League. New outbreak of protest bin dey happun for Prague, and di emperor nephew Ferdinand of Tyrol don dey forced to run.

But Charles V don give instructions on how Saint-Mauris go take "spin" di news for di French court. E say make di ambassador tok say di Prague rebellion na minor affair, and Ferdinand comot di city because e wan join im papa - di emperor brother - on campaign.

For historian Camille Desenclos, di fact say dem use secret codes write some parts of di letters and odas dey for plain language dey important.

"All of dem know say chances dey say di letter go leak. In which case, messages dey wey must reach French," she say - like di fact say di emperor dey cooperate on confidence-building measures for northern Italy.

"Dem leave dis ones for plain language. But oda matas dey wey gatz stay secret - like di true state of affairs wit di Protestant rebellion, dem use code write those ones."

Wetin follow? Only a few weeks later, French king François die, im son Henri II replace am. Charles V defeat di League di following year, but Protestantism don already dey Germany to stay.

For 1552 Henri II form new alliance against di emperor wit di Protestant princes.

And no assassination attempt dey on im life as Charles V die for one Spanish monastery for 1558.