William of Malmesbury made no reference in his surviving works to one of the most dramatic events in the history of the Abbey that he personally witnessed: the deposition by Bishop Roger of Salisbury of Abbot Aedulf in 1118. We only know that this happened because it was recorded in the chronicle known as Annales de Wintonia, which stated that in the immediate aftermath of Queen Matilda's death Aedulf was dismissed ‘without good cause’ from the abbacy of Malmesbury. It is no coincidence that this act was recorded in a Winchester chronicle because Aedulf was a Winchester monk prior to his promotion to Malmesbury. To the profound annoyance of the Malmesbury community, Bishop Roger then became titular abbot and treated the institution as an episcopal priory rather than an autonomous abbey. In the years that followed William of Malmesbury played a central role in a protracted but discreet campaign to question the correctness of Roger's takeover. He began work almost immediately on this project: in around 1119 William produced an edition of the papal history known as Liber Pontificalis, in which he included the full text of the ‘privilege’ of Sergius, the document granting the monastery perpetual exemption from episcopal interference.

During the early 1120s William was working on his major historical works: Gesta Regum and Gesta Pontificum. He used both works to indicate, in a veiled way, that the Malmesbury community rejected the legitimacy of Roger's power over them. In Gesta Pontificum William incorporated the full text of three ancient documents, all of which appeared to indicate that the independence of Malmesbury from episcopal control had been solemnly endorsed in charters granted to Aldhelm. The first was the ‘privilege’ of Sergius. The second was Bishop Leuthere's ‘foundation charter’, which purported to date from 675 and declared that no future bishop should ‘exercise a tyrant's power’ over the monastery. The third document was a charter supposedly issued by Aldhelm himself in 705, which included a directive forbidding future episcopal interference. The ‘privilege’ of Sergius may contain authentic elements, but the other two charters are generally seen as twelfth-century forgeries designed, probably with the collusion of William, to invalidate the claims of Bishop Roger. The Leuthere charter contains a highly suspicious clause forbidding future bishops or kings from meddling in the monastery’s liberties.