It focuses on the Battle of Hastings and its immediate aftermath, although it also offers insights into navigation, urban administration, the siege of London, and ecclesiastical culture.
It is in poetic form, 835 lines of hexameters and elegiac couplets, and is preserved only in two twelfth-century copies from St Eucharius-Matthias in Trier, Bibliothèque royale de Belgique MS 10615-729, folios 227v-230v, and Bibliothèque royale de Belgique MS 9799-809 (the latter containing only the last sixty-six lines).
This theory is suggested by the work praising the allies from France, Boulogne, Ponthieu, Brittany, Maine, and the new Norman kingdom in Apulia, Calabria and Sicily.
In 1066 Bishop Guy may have sought to win royal esteem, possibly damaged by the involvement of Hugh of Ponthieu in the death of King Harold and the senior family's attempts to assassinate the young duke in childhood.
Bishop Guy himself was out of favour with the pope, and it has been suggested that he wanted to garner some Norman influence by writing the Carmen in William's honour and inviting Lanfranc of Pavia, abbot of Abbey of Saint-Étienne, Caen and later Archbishop of Canterbury (to whom the Proem of the poem is dedicated) to use his influence with king and pope.