So ludicrous was the claim made in Da Vinci Code that English was considered la lingua pura and used extensively throughout the Middle Age. Dan Brown seems to claim that this [i]was[/i] the language of the Priory. Seemingly an attempt to push linguistic supremacy for English a millenium earlier !
Latin and French were the tongues most members of European aristocracy, elites, knights, clergy, and scholars spoke. English did not become one of major European languages until 18th century. Ask Godfrey de Bouillon, popes, crusade knights, and even William II King of England and stathouder of the Netherlands in late 17th century any question, and they would reply in Latin and French, as these were their first languages.