The main political and linguistic consequences of the Norman conquest(1066-1515) in English culture were the following:
All the aristocratic system was Normanized. Thus, about 180 foreign barons came to the realm.
Anglo-Saxon and Norman formed the Anglo-Normand state as a single state due to both share the same dynasty and the same aristocracy. As a consequence of that, the kings spent the amount of time in Norman.
England had a trilingual composition during 12th century before the Norman conquest. French was the courtly and literary language. Latin was used for legal documents and for the church. Finally, English was used by common and current people.
There was a leveling of inflection because of there was no learned people of English, so the oral language tends to simplificate.
Old English became Middle English. There was a diverse of dialects but no standards.
As a linguistic consequence of the Norman conquest, we can underline the wealth of French language in the English literature due to French was the leading language in Europe in that time. So, the French literature gave new materials, models and standards for imitation
As a wealth of French language, in literature the old Germanic alliterative verse was substituted by French line that have rhythm.