Having doubtless done some work on the Latin manuscripts on which the Grandes Chroniques de France are based, William wrote a long Chronicon, dealing with the history of the world from the creation until 1300.
Making use of the large store of manuscripts at Saint Denis, William was a compiler rather than an author, and with the exception of the latter part of the Chronicon his writings do not add materially to our knowledge of the time.
[1] In his Gesta Ludovici IX he included a letter from Sempad the Constable to Henry I of Cyprus.
[citation needed] Among his major sources for the reign of Louis IX was the lost Latin chronicle of Primat of Saint-Denis.
A French translation of the Chronicon is in Guizot's Collection des mémoires relatifs à l'histoire de France (Paris, 1823–1835).