Gilles le Breton also known as Gilles the Uniter was the founder and first Royarch of Bretonnia. Gilles was a member of the Bretonni tribes which had many years earlier migrated south just prior to the Battle of Black Fire Pass unwillingly to lend any aid to Sigmar's attempts to defend the Old World against the rampaging Greenskins. By the time Gilles was born the Bretonni clan had inhabited the region which is now Bretonnia for over 900 years.
Ever since the Elves left the region which is now modern-day Bretonnia due to the devastations following the War of the Beard, the region has since been flooded with a number of Greenskin tribes. In 977, after centuries of infighting between the Bretonni, Gilles proceeded to unite the area and drive out the Orcs and Goblins, fighting twelve significant battles. The Brettonian calendar thus begins when Gilles was crowned King of Brettonia, 977 years after the time of Sigmar and the creation of The Empire.
Gilles was killed 18 years after he began his battles by a hurled weapon thrown by one of the remaining Orc Warlords near the edge of Athel Loren. As he was dying he had a final vision of the Lady of the Lake, and his followers placed him on a ship in a nearby lake, where he sailed into the mists to do the Lady's bidding for all eternity. It is said he would return in Bretonnia's most dire time of need, some speculate that he is the mysterious Green Knight fulfilling this vow, which was later confirmed when the latter removed his helmet during The End Times.