What effects did the Norman conquest have on the progression of English?

The Norman Conquest of England in 1066 forever wedded two
cultures (Norman/French) and Germanic/Welsh,Celtic/Scotish/Irish of England and the
surrounding areas. Today, you can see clear indications of French and Germanic influence
in the modern English language. Some English words were replaced with French and
eventually some of the respective grammatical rules blended. Also, the Normans were
“northmen” Vikings who settled in France; so they too were a cultural mix of Norsemen
and French.

William conducted a survey to determine
taxation, called the Domesday (Doomsday) Book. The English aristocracy was replaced. The
Normans created a centralized control over the relatively efficient system of English
‘shires’ which were autonomous and mostly self-governed cells. William and his
successors were vassals to the King of France, but as King of England, William was a
pier with the French King, which led to a tenuous relationship and established a
continuing rivalry between England and France.

The most
obvious difference is in the language. English prominence in its own aristocratic rule
did not return until the 14th century and it would not be until the 15th century that
they stopped speaking French and started speaking what was then Middle English in the
courts.

Check out the links for a comparison between Old,
Middle and Modern English.