The Historia Sicula of the so-called Anonimus Vaticanus, titled by some manuscripts Chronica Roberti Biscardi et fratrum ac Rogerii comitis Mileti, is interesting for two reasons: it offers a useful narrative of the history of southern Italy between the 11th and 13th centuries; moreover, it represents a fairly typical example of historiographical compilation. It lacks an author and a sure title; contains information that partially coincides with the so-called Malaterra; it has a distinctly bipartite textual tradition, in which one branch arrives at the death of Roger I of Altavilla (1101), the second at the beginning of Vespers (1282); has structural inconsistencies; some significant fragments are also incorporated in other texts. This article focuses on the typical processes of aggregative construction of many late medieval chronicles characterized by a low gradient of authorship: they are “liquid texts” par excellence, because they constantly adapt themselves to the multiple needs of other more or less aware chroniclers, compilers, copyists.