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Inside a Medieval Gaelic Castle

A tiny Irish island holds the secrets of an unknown royal way of life

March/April 2020

Ireland Lough Key RockFrom the twelfth to the seventeenth century, the MacDermots ruled the kingdom of Maigh Luirg in the Irish province of Connacht from a small island in Loch Cé (now Lough Key) known as the Rock. They were the right-hand men—and sometime rivals—of the O’Conors, the kings of Connacht, whose power center lay at the modern village of Tulsk, some 20 miles away. It was Diarmait, king of Maigh Luirg from 1124 until his death on the Rock in 1159, who gave the MacDermot clan its name.


In the sixteenth century, the king Brian MacDermot commissioned the Annals of Loch Cé, which remain among the most important written records of medieval Irish history. They are the primary source for the history of the kingdom of Maigh Luirg (Anglicized as Moylurg), which occupied roughly the same territory as the northern section of the modern county of Roscommon. The Annals, which survive in only two manuscripts written primarily in Early Modern Irish, with some sections in Latin, were compiled using earlier Irish annals as sources. They record more than five centuries of political, ecclesiastical, and military events, succession and land disputes, and even notes on the weather. They begin with the Battle of Clontarf in 1014, a contest that pitted Brian Boru, the high king of Ireland, against a coalition composed of the king of Dublin, Sigtrygg Silkbeard; the king of Leinster, Máel Mórda; and a force of Vikings from across the region. The Annals end in 1590, when most of the Gaelic families in Ireland, including the MacDermots, were thrown off their lands by the Anglo-Normans—the ruling class of England after the Norman Conquest in 1066—who had invaded Ireland centuries earlier, in 1169.


Ireland Lough Key MapSurprisingly, there are relatively few references to the Rock of Loch Cé itself in the Annals, or in other contemporaneous historical works. In 1187 (or 1184, scholars are not certain), the Annals record that lightning struck the island, causing a fire. In 1207, the king Tomaltach MacDermot died on the Rock. A further reference is made to a siege of the island in 1235 by an Anglo-Norman force. During the attack, the invaders used siege engines called perriers and fireboats made from demolished wooden houses. The siege forced the MacDermots to abandon the island for a decade. Then, over the next three and a half centuries, the Annals record periodic attacks on the Rock, countless clashes over succession, and the deaths of numerous MacDermot kings. But with only one exception—the mention of a “great, regal house” that was built on the Rock in 1578 by Brian MacDermot—nowhere are the buildings of a royal residence ever described.


The sand-colored stone walls, turrets, and empty windows that can be seen on the Rock today, though picturesque, are not the remains of a MacDermot stronghold, but a product of the imagination of John Nash, the nineteenth-century Welsh architect of Buckingham Palace. In the seventeenth century, an Anglo-Irish noble family named the Kings took possession of the Rock. More than a century later, Robert Edward King commissioned Nash to build the Gothic-style folly, the ruins of which are now visible on the Rock and on guidebook covers, restaurant walls, and travel posters. But it is the MacDermots’ much earlier castle—hidden, perhaps, by crumbling walls, creeping vegetation, and feet of mud—that archaeologist Thomas Finan of Saint Louis University has now set out to find.

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