During the revolt of Prince John "lackland", Lord of Ireland, against his brother, King Richard "the lionheart", in 1193–94, Walter de Lacy joined with John de Courcy to support Richard. De Lacy apprehended some knights loyal to John along with Peter Pipard, John's justiciar in Ireland.[2]
De Lacy did homage to Richard for his lands in Ireland in 1194, receiving his lordship of Meath. After mounting the throne of England in 1199, Prince John wrote to his justiciar in Ireland to complain that de Courcy and de Lacy had destroyed his land of Ireland. Walter had made John his enemy.[2]
In 1206–07, de Lacy became involved in a conflict with Meiler Fitzhenry, Justiciar of Ireland, and de Lacy's feudal tenants for lands in Meath; Fitzhenry had seized Limerick.[3] King John summoned de Lacy to appear before him in England in April 1207.[4] After de Lacy's brother Hugh de Lacy, 1st Earl of Ulster, had taken Fitzhenry prisoner, John in March 1208 acquiesced in giving Walter de Lacy a new charter for his lands in Meath.[4] Upon his return to Ireland later in 1208, de Lacy may have acted as Justiciar of Ireland in lieu of the deposed Meiler Fitzhenry.[5] By this time, John had begun his infamous persecution of de Lacy's father-in-law, de Braose, who fled to Ireland.[5]
On 20 June 1210, King John landed in Crook, now in County Waterford, with his feudal levy and a force of Flemish mercenaries; John marched north through Leinster.[5] When John reached Dublin on 27 or 28 June, de Lacy attempted to throw himself on John's mercy, sending five of his tenants to Dublin to place his lands in Meath back in the king's hand, and disclaiming any attempt to shelter his brother Hugh from John's wrath.[6] John attacked eastern Meath, and was joined by 400 of de Lacy's deserting followers.[6] John would hold de Lacy's lands in Meath for five years.[7]
In 1211 de Lacy erected the castle on Turbet Island in the abortive Anglo-Norman attempt to gain control of West Ulster.
Attempting to secure support in Ireland against the brewing revolt that would lead to Magna Carta, John began negotiations to restore de Lacy to his lands in Meath in the summer of 1215.[7]
Pernel de Lacy (c. 1201 – after 25 November 1288), married Sir Ralph VI de Toeni, Lord of Flamstead, son of Sir Roger IV de Toeni, Lord of Flamstead and Constance de Beaumont.
Gilbert de Lacy of Ewyas Harold, Herefordshire was taken hostage for his father in August 1215. He predeceased his father before 25 December 1230. Gilbert married Isabel Bigod, daughter of Sir Hugh Bigod, 3rd Earl of Norfolk (Magna Cartasurety) and Maud Marshal. They had a son and two daughters:
Walter de Lacy, who married Rohese le Botiller but had no issue. De Lacy died between 1238 and 1241.