This two-volume luxury Bible was commissioned by Leonello d'Este's brother Borso (1413-1471). Stylisitically Borso's Bible appears to bear little relationship to Leonello's Breviary, but it's replete with family insignia, and the history of the Bible is well documented. In 1598 it moved with the rest of the d'Este collection to Modena, when Pope Clement VIII claimed Ferrara for the Papal States. The Bible remained in Modena until 1859, when war in Italy caused Archduke Francis d'Este-Austria to flee to Austria. The Bible of Borso survived this relocation, but the Breviary of Leonello d'Este was separated from the collection sometime before this, as documented by John Allan Rolls (1776-1837), who referred to the manuscript as "Peninsular Loot," purchase by his grandfather, who died in 1837.
In contrast to Borso's Bible, the so-called Missal of Borso d'Este reflects a different aesthetic that conforms closely to the Llangattock Breviary, so much so that it appears to have been made as a companion piece to the Breviary and commissioned from Leonello but completed after his death in 1450. This missal has yet to be studied in depth, but should be considered in any stylistic and physical analysis of the Llangattock Breviary. Not only can the illumination can be attributed to Giorgio d'Allemagna and his team, but the script is identical to that of the Llangattock Breviary. Moreover it contains fully illuminated pages with half-page miniatures that may reflect those once part of the Llangattock Breviary, but according to John Allan Rolls, were "cut out by soldiers."
This manuscript, the Breviary of Ercole d'Este (1431-1505), Leonello's half-brother, follows a liturgy that closely conforms to that of the Llangattock Breviary. This manuscript has been referred to as a benchmark text throughout this project, not only to better predict the textual organization of the Llangattock Breviary, but also to identify specific leaves, which often include little or no rubrication. The best and most reliable way to identify the Breviary's detached leaves is not by collection or repository, which are unstable and many times unknown, but by the exact recognition of the text on the leaf, such as "Feast for the Octave of Easter, Terce-2nd Vespers; Feria 2, Matins-Lauds." Too few catalog descriptions of Llangattock leaves provide this, and yet it is the most necessary information required to reconstruct the manuscript, one leaf at a time, according to the continuity of the text.