Sometime after 1066 (probably in the 1070s), William started writing an account of the deeds of his patron. It is called Gesta Guillelmi ducis Normannorum et regis Anglorum ("The Deeds of William, Duke of the Normans and King of the English"). It is the earliest biography of a decent length of any Norman duke, and gives details on the Battle of Hastings. As a chaplain attached to the duke's household and a trained knight, William was in a unique position to relate the events of the duke's preparations for and execution of the war to conquer England.
To be fair, there are several passages that disproportionately praise or favor the duke' actions. When Orderic used the Gesta Guillelmi as a source for his own history, he left out those sections. William also follows medieval literary tradition by describing Duke William as the perfect embodiment of knighthood, with exploits such as the duke and 50 knights besting 1000 of the enemy. He also compares the duke's conquest of Britain to another famous conquest of Britain, that of Julius Caesar.
There are comments made by William that are unique to his account of the times that modern historians feel are accurate statements. Some are the notion that Harold had abundant treasure, and that a Danish raiding party gained "great booty"; this all suggests why England was such a target for raids in the 10th through early 11th centuries.
William also provides an account of early pre-conquest Norman society, with several rebellions in Normandy, as contrasted with the relative stability of England, where William says the English all showed love of their country and a stronger national identity and unity.
The fractured nature of the Norman culture was explained by a Benedictine monk in the 11th century. Tomorrow we'll look at the origins of Normandy, and why this land south of England was named for "North Men."