Orpen's magnum opus was originally published in two volumes in 1911, and a further two in 1920 - a total of some 1500 pages. Clarendon Press subsequently reissued the four volumes in 1968. It remains unsurpassed to this day. This new Four Courts Press edition, which is printed in one volume, incorporates the original pagination so that readers can refer to the earlier edition with ease. The book itself deals with events in Ireland from the Cambro-Norman invasion of 1169 to~the portentous murder of the earl of Ulster in 1333 as the history of a number of regions, rather than focusing exclusively on the concerns of the English king's administration, but his example has never hitherto been followed in relation to the Anglo-Irish colony. Although the project had its detractors (most notably Eoin MacNeill, who held the Chair of medieval history in UCD in 1909), it remains the definitive work on the period.