After Henry captured and imprisoned William's father, Duke Robert, he placed his nephew, William in the custody of Helias of Saint Saens, count of Arques. Helias had married a natural daughter of Duke Robert, and consider him his friend and patron.

William stayed with Helias and his sister August 1110. Suddenly King Henry sent agents to demand that the boy be brought to him. Helias was not at home at the time, so his family hid William and smuggled him to Helias, who fled the duchy and took him to Robert de Belleme who owned many estates south of the duchy. Because he did this, the king took Helias' lands. King Henry captured Robert in 1112 and Helias took William to the court of Count Baldwin VII of Flanders. He was William's cousin. By 1118 the Norman counts and barons were not satisfied with King Henry and they became an ally of Cunty Baldwin and started a very dangerous rebellion on behalf of William Clito.

They seized quite a bit of the duchy in the north. At the siege of Arques in September 1118, Count Baldwin was seriously injured and the campaign ended. In Aug 1119, Louis VI of France took up the cause of William Clito and invaded the duchy on the river Seine. He was met by King Henry's troops and was defeated at the Battle of Bremule. William barely excaped capture when he rode as a new knight that day. King Henry's son, William, sent him back the horse had had lost in the batle. Louis brought William Clito's case to the pop in October 1119 at Reims and Henry I had to justify how he had treated the boy.

William Atheling died on 25 November 1120 and he was the only legitimate son of King Henry I. William Clito was the obvious heir to England and Normandy. He had married Sibylla of Anjou, daughter of County Fulk V of Anjou. She would bring the county of Maine as her dowry. King Henry appealed to canon law and the pop annulled their marriage in August 1124 because the couple were within the progibited degrees of kinship.

In Normandy, rebellion broke out in favor of William Clito. However they were defeated at the Battle of Bourgtheroulde in March 1124. Henry had his son-in-law, Emperor Henry V who had married his daughter Matilda, to threaten Louis from the east. The emperor called off his invasion of France in 1121, when confronted by a large force under Louis VI at Rheims.

In January 1127, Louis VI granted William Clito the royal estates in the French Vexin. He could use these as his base to attack down the River Seine into Normandy. He also wanted to free his father from his long imprisonment and recover his ancestral inheritance. He married the queen's half sister. When Count Charles the Good of Flanders was murdered on 2 March 1127, it gave King Louis a much better chance to help William Clito. King Louis took his army into Flanders and got the barons to accept William as their new count.

William did well at first. He secured most of the county by May. However a rival emerged in Thierry of Alsace which led to deterioration of his position. St. Omer and Ghent when against him in February 1128 as well as Bruges and Lille by May. They welcomed Thierry and William did not have much control left. He had only the southern fringe of Flanders. However, William, with his norman nights and French allies, he struck back and defeated Thierry.

William was then jouned by Duke Godfrey of Brabant, his father in law, and their armies siezed Aalst on 12 Jul 1128. They intended to reduce Ghent. However, William was wounded in the arm during a battle with a foot soldier.