O’Neill, seeing his brother-in-law fall under evil influences, tried to enforce payment of his rent by “distress.” In 1606 he resumed possession from O’Cahan of the fishery of the Bann, and took a prey of his cattle. This dispute was greedily welcomed by the enemies of the chiefs. O’Cahan lodged a protest with “the State” against the seizures; and O’Neill, although the King gave him sovereign control in his territory, was cited to appear before the Privy Council in Dublin to answer Sir Donal’s complaint. A splendid opening for the spread of the Gospel loomed in sight of the “reformers.”

When the case came on the Deputy majestically presided over the Council as supreme judge. The suit concerned a river for which, a year earlier, he issued a Patent to Hamilton, and then had it conveyed to himself. Montgomery attended the trial to give it a spiritual solemnity and support O’Cahan. Without at first entering deeply into the merits, Chichester—to gain time to prejudice the King—ordered O’Cahan to send in a formal petition and O’Neill to lodge a written reply. He then appointed the Attorney-General (Davies) and the Solicitor-General (Jacob) to act as counsel for O’Cahan, and adjourned the trial for a month. O’Neill, bereft of legal assistance, was left to his own devices. Before the next hearing Davies sent a report on the case to Cecil. He threw out that O’Neill’s Patent was bad, but spared mention of the fact that a petition for its amendment had been rejected on his advice—although in other cases “defective title” was cured for the asking. Nor did the Attorney-General relate that the Bann had been seized by the Deputy, or that he sat, and would again sit, to try the title to its waters without informing the litigants that he held spurious Patents for it in his pocket.

In June, 1607, the Court re-assembled in Dublin Castle, and Davies at once raised objections to O’Neill’s grant. He argued that, notwithstanding the treaty of Mellifont, “Tyrone” did not include “O’Cahan’s Country”: and, therefore, that the Earl’s seizures from his vassal were unlawful. As no map was attached to the Patent (which embraced several counties) it was easy to wrangle over boundaries. The Deputy and his confederates patiently listened to the Attorney-General. They thought his contention ingenious; although it was marred by the blot that its logic required a decision in O’Cahan’s favour. This would no more have suited than a victory for O’Neill. Sir Donal had served his turn. Davies, therefore, also argued that the Earl’s Patent was altogether bad. True, he was the lawful heir to Tyrone under a prior Patent to his grandfather, Con, from Henry VIII.; but that did not count, for had he not risen in rebellion against Elizabeth? His subsequent pardon by King James without attainder was not to be made too much of; and Davies rattled on by the hour berating the fallen chief. Chichester gloated over his victim’s plight; chid him betimes when he exploded against his adversary; and in the end gave judgment against both of them. This feat was unexpected by Sir Donal, but the decree was ingenious. It ran:—“Upon examination of the whole matter, it seemed to them that the right to that country still remaineth in his Majesty.” In other words, the Treaty of Mellifont was broken, and O’Neill’s Patent was declared void. Punic faith was honour bright with Sir Arthur Chichester.

A trap was then laid for the Earl by a proviso that, until his Majesty’s pleasure should be signified, O’Cahan was to have two-thirds of the lands, and the Earl one-third, but that meanwhile O’Neill was to repair to London before the following November, to await the Sovereign’s pleasure. As to the Bann, the decree was marvellously mute. Davies wrote to prepare Cecil for his victim’s visit, and make up the King’s conscience. His falsehoods, dated 1st July, 1607, were plenary:—“Plainly neither of them hath any title. It is now, and ever hath been, vested in the actual possession of the Crown since the 11th Elizabeth. Howbeit, the land lying in those remote parts, the ignorance and negligence of officers was such that it was never brought into charge.” All this, four years after the Patent of 1603, and the pardon from James I. which alone would have revived his rights (as grandson of Con O’Neill) under the Patent of Henry VIII.

After such a trial O’Neill felt that the command to proceed to London covered a plot to get rid of him altogether. London held a grim keep called the Tower, familiar to the owners of Irish estates, whither scores of chieftains had been lured aforetime. His experience disinclined him to make the pilgrimage. He knew that the Deputy had clouded the King’s mind with suspicions as to his loyalty, and he brooded over some earlier essays to compass his assassination. The dungeon or the scaffold was, he feared, to end the trip to Court. An estate so unwholesomely extensive as his forbade much hope of justice. The partition of Sir Con O’Neill’s patrimony in Claneboy was not two years old, and the alliance between Hamilton, who contrived it, and the Deputy, who abetted it, remained in full force. The Earl, therefore, came to the conclusion that he was a doomed man, whether he went to London or whether he remained at home. He took counsel at Mellifont with Sir Garret Moore (who had persuaded him to sign the treaty of 1603), and resolved to go into exile. Then he bade farewell to Moore, and having also taken leave of the Deputy at Slane, O’Neill, in September, 1607, sailed for France from Rathmullen, with Maguire, Lord of Fermanagh, O’Donnell, Earl of Tirconnell, and their kinsfolk. Such was the terror of Chichester that they were denied water for their ship in one creek in Donegal.

Bards and Brehons have lamented that these Gaelic lords did not hold their ground. Their critics have not explained whether the Earl of Tyrone should have gone to London and risked being mewed up in the Tower, or have disobeyed the order and resisted arrest without an army to back him. The victim himself, living and acting in days when he could measure and appreciate the consequences of obedience or revolt, decided on flight. It may not have been a heroic course, but it was a decision taken by a seasoned captain, who had faced death on a score of battlefields, and whose deeds of daring still rang throughout Europe.