Book 5 chapter 410 of William of Malmesbury's Gesta Regum Anglorum, which describes the mostly forgotten crusade of Sigurd, co-king of Norway, in 1106/8–10, contains a curious vignette about the emperor's sojourn in Constantinople:

Although at first one might pass over this passage as an oddity, the fact that it is only found in William's text encourages closer examination. Sigurd's crusade is mentioned – very briefly – by only two other Latin chroniclers, Albert of Aachen and Fulcher of Chartres, but this episode is absent from their histories. Moreover, it is not described in the vernacular sagas that record Sigurd's crusade in detail; these concentrate instead on Sigurd's good relations with the Byzantine Emperor, Alexius Comnenus. Sigurd's crusade has been mostly forgotten since its military impact was fairly limited, and indeed William does not dwell on Sigurd's sieges of Tyre and Sidon. How and why, then, did this episode make its way into William's text, and how should we interpret it? If we consider William as an historian of crusading, the twelfth-century medical context in which he wrote, and his other discussions of medical incidents occurring during the crusades, we will see that he was a chronicler with a very keen interest in medical experiences, whose discussion of them could contain subtleties relating to the importance of leadership, place and the crusading endeavour.

William has been somewhat overlooked as an historian of the crusades because of the relatively late date of the composition of the Gesta Regum in relation to other narratives of the First Crusade, and William's reliance on other written sources. However, recent trends in the study of medieval chroniclers, including those narrating the crusades, suggest that these reasons for excluding William from crusading scholarship are no longer valid, if indeed they ever were.