When Henry II granted the province of Meath to Hugh de Lacy in 1172, the Anglo-Norman lord received theoretical control over a vast territory encompassing modern-day Meath, Westmeath, Longford, and much of Offaly. De Lacy chose this strategic riverside location as the administrative centre for his new domain, envisioning a castle that would serve as both an imposing defensive stronghold and an impressive symbol of Norman authority.

Before the famous stone keep that visitors see today could rise from the ground, de Lacy needed to secure the site quickly. Archaeological excavations in the 1990s revealed that the earliest fortification was a circular ringwork, approximately 45 metres in diameter, defended by a wooden palisade and surrounded by a substantial fosse up to 10.5 metres wide. According to the Norman-French poem ‘The Song of Dermot and the Earl’, this initial timber fortress barely survived its first year; Ruaraí O’Conor promptly burnt it down, forcing de Lacy to rebuild immediately. Evidence of this dramatic episode survives in the archaeological record, with burnt palisade posts and the remains of a large granary that went up in flames during the attack.

The second timber phase proved more successful, featuring a rebuilt palisade with posts connected by slot trenches and backed by a wooden wall-walk that would have given defenders a proper fighting platform. This reconstruction bought de Lacy the time he needed, and by 1175, work began on the magnificent stone keep that would transform Trim into one of medieval Ireland’s most formidable castles. While some 19th-century accounts mistakenly dated the castle to 1220, modern archaeological investigation has confirmed that Hugh de Lacy’s ambitious building programme began in the 1170s, establishing Trim as the beating heart of Norman power in the Irish midlands for centuries to come.