This study backs the belief that language change arises in the spoken mode before diffusing to the written mode, by collating the language of the Year Books, texts attesting to oral medieval court pleading, and comprising elaborate dialogue, and of legal register written-mode origin texts, in Medieval English Parliament Rolls. Both tekst sets were written in Anglo-Norman, emerged within a rather homogenous speech community, and comprise the same time period – late 13th century until c. 1350. Changes known to have appeared in later medieval French are confirmed at this time in the dialogic texts, but to a minor extent or not at all in the written register texts.