was, and usually the number of peasants, ploughs, and any other resources the holding had. Towns were listed separately. All the English counties south of the River Tees and River Ribble are included, and the whole work seems to have been mostly completed by 1 August 1086, when the Anglo-Saxon Chronicle records that William received the results and that all the chief magnates swore the Salisbury Oath, a renewal of their oaths of allegiance. William's exact motivation in ordering the survey is unclear, but it probably had several purposes, such as making a record of feudal obligations and justifying increased taxation. Death and aftermath William left England towards the end of 1086. Following his arrival back on the continent he married his daughter Constance to Duke Alan of Brittany, in furtherance of his policy of seeking allies against the French kings. William's son Robert, still allied with the French king, appears to have been active in stirring up trouble, enough so that William led an expedition against the French Vexin in July 1087. While seizing Mantes, William either fell ill or was injured by the pommel of his saddle. He was taken to the priory of Saint Gervase at Rouen, where he died on 9 September 1087. Knowledge of the events preceding his death is confused because there are two different accounts. Orderic Vitalis preserves a lengthy account, complete with speeches made by many of the principals, but this is likely more of an account of how a king should die than of what actually happened. The other, the De obitu Willelmi, or On the Death of William, has been shown to be a copy of two 9th-century accounts with names changed. William left Normandy to Robert, and the custody of England was given to William's second surviving son, also called William, on the assumption that he would become king. The youngest son, Henry, received money. After entrusting England to his second son, the elder William sent the younger William back to England on 7 or 8 September, bearing a letter to Lanfranc ordering the archbishop to aid the new king. Other bequests included gifts to the Church and money to be distributed to the poor. William also ordered that all of his prisoners be released, including his half-brother Odo. Disorder followed William's death; everyone who had been at his deathbed left the body at Rouen and hurried off to