 Significantly, the fortress was built on the remains of an old monastic site, which has led some historians to wonder whether a similar thing might not have happened at the ecclesiastical enclosure of Duiblinn.The annals are silent as to the ultimate fate of the latter settlement and its community – no Abbot or Bishop of Dublin is mentioned after 785; the possibility remains that it was abandoned in the late 8th century before the arrival of the Norsemen, who simply annexed it and built their "longphort" on the site.In 867 a force led by the king of Loígis Cennétig mac Gaíthéne burned the fortress at Clondalkin and killed 100 of Amlaíb's followers.