In August 1189 William Marshall married Isabel de Clare, heiress of Richard de Clare, otherwise known as Strongbow, and through his wife came to be one of the greatest Anglo-Norman landowners in Ireland. The couple would have ten children, five of them sons, which would seem to have secured the family’s future, except for a bishop’s curse. At some date between 1207 and 1213, Marshall, by then Earl of Pembroke, seized two manors belonging to Albin O’Molloy (Ailbe Ua Maíl Mhuaidh) and refused to return them. For this slight, O’Molloy excommunicated him and, in the aftermath of Marshall’s death, when his children still held onto the manors, the bishop is supposed to have laid a curse on them, declaring that none of the sons would have heirs and that the great Marshall estates would be scattered. And so it came to pass: although each of the five brothers became Earl of Pembroke, they all died without legitimate children and eventually their father’s property was divided between their sisters and the latters’ children, leading to the break-up of the great Marshall estate, just as the Bishop of Ferns had declared. 

Around 1207 Maud, eldest daughter of William Marshall and Isabel de Clare, married Hugh Bigod, third Earl of Norfolk: incidentally, it was through this marriage that the position of Earl Marshall of England would come to be held by the Dukes of Norfolk. Furthermore, as a result of the marriage, the Bigods came to own large areas of land in what is now County Carlow and when Roger, fifth Earl of Norfolk visited Ireland in 1279, it is thought that he embarked on constructing a large stronghold for himself, now known as Ballymoon Castle, the remains of which can be seen here. In his book on the Bigods during the 13th century, Marc Morris proposes that the building’s purpose was not intended to be defensive. ‘Built on a scale which presupposes a patron in need of extensive accommodation and with considerable resources at his disposal,’ Ballymoon was ‘intended to function as a residence more than a fortress.’ Morris points out that there is no ditch around the site and no projecting towers; the only breakfronts on the walls contained latrines. A cousin of the MacMurroughs, with whom he seems to have been on good terms, Roger Bigod did not face militant opposition on Carlow, hence there was no need for a protective citadel. 

Ballymoon Castle consists of a single square courtyard about 80 feet long on each side, the rough-hewn granite outer walls being some eight feet thick at the base and climbing 20 feet, although their uneven appearance indicates they were once higher and perhaps finished with crenellations and walks. The big, empty courtyard has the remains of buildings on each of its four sides, some of which indicate where doors or chimneypieces were once placed. The western wall has an arched gateway with portcullis grooves visible, and there are quite a few cross-shaped openings around the other walls. It may be that work here was never finished: by the autumn of 1280 Roger Bigod was back in England. And two years later, his cousins, Art and Muchertach MacMurrough, were murdered in Arklow on the instructions of the Justiciar of Ireland, Stephen de Fulbourn. When Roger Bigod died in 1306, despite two marriages, like his Marshall forebears he had no heirs, so the direct line ended, his lands were escheated to the crown and eventually bestowed on Thomas of Brotherton, Earl of Norfolk, a younger son of Edward I. Little is known thereafter of Ballymoon Castle’s history, but, having little defensive potential, it would appear to have been abandoned and left to fall into its present condition.