In 1272, Hugh de Lacy was granted the Liberty of Meath by Henry II who sought to limit the expansionist policies of Strongbow [Richard de Clare], whom he feared might set up an independent Anglo-Norman kingdom in Ireland. Soon after his arrival at Trim, de Lacy built a wooden castle, the spike stockade mentioned in the "Song of Dermot and the Earl"--a poem of the period.
De Lacy left one of his barons, Hugh Tyrell, in charge, but when O'Connor, King of Connacht, threatened, Tyrell abandoned and burned the castle. By 1176, this wooden fortification had been replaced with a stone keep or tower. When the site was secure, the castle yard was surrounded by curtain walls and moat with a simple gate and bridge to the north. Analyses of samples of surviving structural timbers show that the keep was extended in at least two more phases and remodelled in the lifetime of Walter de Lacy, Hugh's son. Later, fore-buildings were built to protect the entrance to the keep. [Trim Castle Visitors Guide, Duchas--The Heritage Service of Ireland]
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Hugh was killed in Durrow while overseeing the building of a smaller castle. A man, who had gotten close to Hugh pulled an axe from under his cloak and lopped Hugh's head off. His body was buried at the Bective Abbey about 8 kms. from Trim Castle while his head was buried near his 1st wife in Dublin. The Cistercian Monks of Bective Abbey had hopes that the possession of Hugh's body would give them rights to Trim Castle and the extensive lands associated with it. However the king took the castle and lands until Walter came of age, at which time Richard I gave them to Walter.