A more thorough explanation:

Norman French is a language that was spoken by the Normans. It became the official language of English courts after the Norman Conquest in 1066. The language deteriorated into Law French and continued to be used until the late 17th century. English became the official language of the courts in 1731.

For example, when William the Conqueror became the King of England in 1066, he brought with him the Norman French language. This language was used by the ruling class and in the courts. Over time, the language changed and became known as Law French. It continued to be used in the courts until English became the official language in 1731.

Another example is the Magna Carta, which was written in Latin and Law French in 1215. This document was an agreement between King John and his barons, and it established the principle that everyone, including the king, was subject to the law.

These examples illustrate how Norman French was an important language in the history of England and how it influenced the development of the English language.