The version of the "Gesta Herewardi" which exists today is a transcription of this work, which was incorporated into a book containing charters and other material relating to the abbey at Peterborough known as the "Register of Robert of Swaffham", though variant descriptions such as "Robert of Swaffham's Book" are also found. According to the historian Janet D. Martin, the book was created in "about 1250", and originally ended with the "Gesta Herewardi", but further material, unrelated to the Hereward story, was added in the 14th century.