It was written in the language of the people. The rulers of Britain at that time still spoke the Norman French they brought with them in ten sixty-six.
VOA: special.2011.01.12
In 1066, the Norman invasion established French as the language of government, but it did not dislodge English.
Two centuries of Norman rule in England after 1066 significantly changed the Germanic grammar and dumped a large amount of French vocabulary into the language.
