Ernoul
Also known as Ernoul of Ibelin

Squire to Balian of Ibelin and the eyewitness Frankish voice for the Hattin year — his Old French chronicle, surviving inside the later Chronique d'Ernoul et de Bernard le Trésorier, is the partisan but indispensable counterweight to the Latin sources for 1187.
Almost nothing is known about Ernoul beyond what he tells us himself: that he was a young squire in the household of Balian of Ibelin, that he was at the rearguard with his master at the disaster of Hattin in July 1187, and that he was present at the surrender of Jerusalem to Saladin three months later. Some scholars have tentatively identified him with the later Frankish lord Arneis of Gibelet; others doubt this. He survives, like a great many medieval witnesses, only as the voice of his own pages.
The text he wrote is now embedded in a longer composite chronicle, the Chronique d'Ernoul et de Bernard le Trésorier, but the Hattin section preserves the perspective of the Ibelin party — sympathetic to Raymond III of Tripoli and his peace policy, harshly critical of Reynald of Châtillon and the new King Guy whom they blamed for the catastrophe. It is also the source for some of the unforgettable particulars of that summer: the True Cross carried into the field on the morning of the battle, the prisoners stripped and roped together in the heat, the long bargaining over the ransoms in besieged Jerusalem.
Ernoul's chronicle was reworked into Old French and used by the continuators of William of Tyre as the backbone of their account of the years 1184–1228, which means that through this anonymous squire the partisan Ibelin reading of the Hattin disaster shaped most of what later medieval Europe believed about it.
Read more on Wikipedia: English article