Final answer:
King William, also known as William the Conqueror, was the first to claim all of England as his personal property after his victory at the Battle of Hastings in 1066.
Step-by-step explanation:
The first king to claim all of England as his personal property was King William, also known as William the Conqueror. This occurred during the High Middle Ages, after William, Duke of Normandy, successfully took control of the English throne through the Battle of Hastings in 1066.
His claim over England was solidified when he became king, starting a new chapter in the country's history filled with disputes over legitimate rule. His assertion of power was a significant shift from the earlier division of England into separate kingdoms such as Wessex, Mercia, and others that were continuously challenged by outside forces.