Castell Aberlleiniog was a motte-and-bailey fortification raised circa-1088 by Robert of Rhuddlan. This substantial fortress was attacked by Gruffudd ap Cynan in 1094 and destroyed. The abandoned earthworks were re-occupied during the seventeenth century and later a stone structure, possibly a folly, was constructed on the summit.
Throughout the medieval period the rich fertile lands of the Isle of Anglesey served as the breadbasket for Northern Wales. This made the island strategically important prompting the Normans to invade in 1088 under the command of Robert of Rhuddlan, a retainer of Hugh de Avranches, Earl of Chester. The native Welsh lord, Gruffudd ap Cynan, was overthrown and Castell Aberlleiniog was raised to secure the area.
The castle was an earth and timber motte-and-bailey fortification. The mound, which was raised on top of a natural hillock, would have been topped with a wooden palisade and was separated from the bailey by a deep dry ditch. A narrow bailey extended to the south and had strong natural defences due to the steep scarp down to the Afon-y-Brenhin. A small mound closer to the straits may well have been a watchtower or some other associated structure.
Although imprisoned by the Normans immediately after his overthrow, Gruffudd ap Cynan was at liberty in 1094. He invaded Anglesey the same year, stormed the castle and burnt the structure. The castle was never rebuilt and, when the Normans invaded again two centuries later, Beaumaris Castle was built on a new site further to the west.
The abandoned motte was re-occupied during the seventeenth century Civil Wars when Thomas Cheadle, Constable of Beaumaris adapted the site into an artillery fort to control the Menai Straits. It is unknown whether this fort included the stone revetting and towers seen today as these may have been added later as a folly. Today the stone structure is known as Lady Cheadles's Fort.
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Castell Aberlleiniog consists of the remains of an eleventh century Norman motte-and-bailey fortification. Destroyed shortly after it was raised, the site was re-occupied in the seventeenth century and Lady Cheadle's Fort constructed on the summit.
Castell Aberlleiniog. The impressive motte was raised before 1093 by Hugh of Avranches, Earl of Chester.
Lady Cheadles's Fort. Folly or fortification? It is uncertain whether the stone structure formed part of the seventeenth century artillery fort or was simply a later folly.