Compared to the ‘Annals of Ulster’ and the ‘Annals of Loch Cé’, the Clonmacnoise-group texts known as the ‘Annals of Tigernach’ and Chronicum Scotorum present a greater task for the historian trying to reconstruct their texts in the tenth and eleventh centuries, because they differ considerably from each other. The main task is to determine what material came from their common source, and what was altered, added or lost. Only then can other issues, such as the sources of the common source and its relationship to the ‘Chronicle of Ireland’, be addressed.

The main detailed study of the Clonmacnoise-group texts in this period has been undertaken by David Dumville. Dumville argued that a ‘Clonmacnoise Chronicle’, continuing the ‘Chronicle of Ireland’, was in existence by 911×54, and that AT and CS derive from a common source written ca 1113 or later. However, Dumville was uncertain whether AT and CS were simply versions derived from a common source dating from between ca 1150 (when CS ends) and ca 1350 (when the manuscript of AT was written), with one of either AT and CS having been rewritten, or whether in the twelfth century (and from examples given, perhaps the eleventh) AT and CS may represent two different chronicles maintained in Clonmacnoise in close contact with each other, also perhaps with some different source material for the eleventh century.