Within Medieval England, Feudalism became a normal way of life and stayed that way for centuries afterwards.
William I is more famously referred to as William the Conqueror. He managed to defeat Harold’s English army but had to gather total control of England first before he was able to be properly accepted as the King of England. Essentially he was a foreigner who had forced his way to London, so was not exactly well liked among the population of England and he reverted to force to keep his control over England.
It was physically impossible for William to rule the whole country himself, as 11th century travel was slow and challenging and slow. William was still the Duke of Normandy and had to go back to Normandy to maintain control of this French land. So this meant he had to be out of the country for several weeks at once. He also needed a method to control England, ensuring the people stayed loyal.
William spent a lot of time in London and built his own castle - otherwise known as the Tower of London - and this overlooked the city. He additionally built Windsor’s first castle where the motte can still be seen. The nation of England looked upon castles as a clear threat - simply because they had soldiers in them to be used in defence of the English if they caused any trouble.
However, William also required a way to govern the country overall, which led to him introducing the Feudal System.
William split England up into vast sections of land which were similar to today’s counties. These were 'given' to noblemen who heroically fought for him in battle. William’s argument was that those who were prepared to die for him in battle would prove loyal as well. However, the nobles did not just receive the land automatically - first they were required to swear an oath of loyalty to William, collect the taxes for him in their region and supply soldiers to the king if they were requested. In the 11th century, swearing on the Bible was very important and not many would even dare breaking this as they believed they would be condemned to Hell if they did. The men who received these land packages would be barons, earls and dukes - generally the most highly regarded person within their local area. In the Feudal System context, these men were referred to as tenants-in-chief.
These portions of land were still big in size and tough to maintain - the barons etc divided up their land even more which were 'given' to trustworthy Norman knights who also fought battles well. Knights were individually assigned a section of land to govern and were required to swear an oath to the baron, duke or earl as well as collect taxes when ordered and supply soldiers from his own land when needed.
The argument was that since they had each sworn an oath to their baron, in reality they had sworn an oath to the king. The lords made sure to constantly keep law and order - those in their land or manors were badly treated and there remained a continual threat of Norman soldiers being used in opposing the English people wherever they were living. The lords needed to do a good job otherwise if they were unsuccessful, they could be withdrawn from their position. They had a simple role - make sure the English were kept in their place, under Norman control. These men (the knights) were labelled sub-tenants under the Feudal System.
Both groups were official tenants - meaning a word associated with land which is not someone’s property. Both essentially rented out their land by the provision of money or services to the land’s true owner - in this case, William the Conqueror.
Last were the English who had been conquered and had no choice but to obey commands or pay a price for disobeying.
It is obvious that William was a harsh ruler, but at the same time he had also taken the country. Him being in England was not due to the people’s majority vote so he had to make sure that he always had total control over them. He maintained visible signs of his power through building a lot of Norman castles. He was also aware of what he was owed since he commanded to have a survey of the entire country - known as the Domesday Book.
See also: Feudal Services
"Feudalism". HistoryLearning.com. 2015. Web.