This tower house, occupied by Thomas Fleming in 1561, became the setting for a crucial parley during the Nine Years’ War. In September 1599, Hugh O’Neill, Earl of Tyrone and leader of the Irish rebellion, spent two days in negotiations with Richard Devereux, Earl of Essex and Lord Lieutenant of Ireland, at what was then known as the castle of Garret Fleming. These talks followed their initial encounter at the ford of Bellaclinthe and represented a significant moment in the conflict between Gaelic Ireland and English rule.

The castle remained visible as late as 1836, when the Ordnance Survey Name Books recorded its ruins still standing on the riverbank. A particularly notable feature was a stone carved with the Fleming coat of arms, which survived at the site and served as a tangible link to the family who once controlled this strategic location. The Flemings, an Anglo-Norman family who had settled in the area during the medieval period, maintained their presence here for centuries, with the castle serving as both their residence and a symbol of their local authority.

Today, no visible trace remains of Lagan Castle above ground, leaving only historical records and archaeological surveys to tell its story. The site represents a lost piece of Ireland’s architectural heritage; a place where the political tensions of the late Tudor period played out in diplomatic negotiations that would ultimately fail to prevent Essex’s downfall and O’Neill’s continued rebellion. Though the physical structure has vanished, the location remains significant as a reminder of how even modest tower houses could become stages for events that shaped the course of Irish history.