William's eldest son Robert was known as Robert Curthose, meaning 'short trousers'. This unflattering nickname was given to him in childhood, possibly by William. He had a number of disagreements with his father and tried to take the crown of England from his brother, William Rufus.

Robert Curthose spent the years 1077 to 1080 effectively at war with his father. This was because he wanted more power than William was prepared to give him.

• ❖ In 1077, Robert and his army tried to take control of Rouen Castle after Robert's brothers played a prank on him and he felt William didn't punish them harshly enough.
• ❖ Robert fled to Flanders and was given a castle on Normandy's borders by the King of France. Robert launched raids against his father's land.
• ❖ William raised an army against him, but Matilda secretly sent him money, which caused a huge argument between them.
• ❖ They fought each other in battle in 1079. Robert knocked William off his horse, then gave him his own horse and ordered him to retreat. William was humiliated.
• ❖ Matilda organised a meeting between them in 1080. William made Robert the heir to Normandy again.

Robert became Duke of Normandy when William the Conqueror died, but he wanted the throne of England which had gone to his brother, William Rufus.

• ❖ Norman custom generally stated that the eldest son inherited all his father's estates.
• ❖ Many Norman lords owned land in England and Normandy, and would have preferred a single ruler over both.
• ❖ His uncle, Bishop Odo, stirred up rebellion on behalf of his claim, but Robert did not come to help him when he was besieged in Rochester Castle.