Shortly after Henry left Ireland, Hugh de Lacy invaded Meath, setting up countless motte and bailey fortifications throughout the kingdom. de Lacy made the ecclesiastic centre of Trim his stronghold, constructing a huge ringwork castle defended by a stout double palisade and external ditch on top of the hill. With de Lacy now at the border of Ua Ruairc's outermost settlement of Kells, a parlay was arranged and the two leaders met on the Hill of Ward for negotiations. During these negotiations, a dispute erupted and de Lacy's men killed Ua Ruairc. Both sides blamed the other, with the Irish annals reporting that Ua Ruairc was ""treacherously slain"".