This article is the first step in a new study of the text known as the Chronique du Bec, known from a fifteenth-century medieval manuscript produced in this abbey, and from copies dating from the modern period, which have served as the basis for several editions (Luc d'Achery, Adolphe-André Porée). It begins with a new examination of the text's traditions and a description of the manuscript Reg. Lat. 499 preserved in the Vatican Apostolic Library, including in a codicological perspective. One of the achievements is to demonstrate that Luc d'Achery's edition cannot be considered as fully representative of a medieval version of the text. Through a study of the content of the chronicle and its placement in the historical context of the abbey of Le Bec, the second part of the article seeks to identify the phases of writing that were sedimented in the fifteenth-century manuscript, thus opening up a number of paths for exploring the writing of history at Le Bec (for example, by exploring the silences in the chronicle) and the links between historical writing and other forms of documentary production.