1109. Traditionally, the author of the anonymous work has been given as Richard or Thomas, two monks at Ely, one of whom, Richard, has been identified with an official of the monastery, but some historians hold that neither Richard nor Thomas was the author.

The Liber covers the period from the founding of the abbey in 673 until the middle of the 12th century, building on earlier historical works. It incorporates documents and stories of saints' lives. The work typifies a type of local history produced