The Lament for Owen Roe

In the face of a potential landing by a large expedition of English troops, O'Neill quarreled with his rival Catholic commanders and refused to accept the Treaty.

His temporary alliance with the English having broken down, O'Neill now reached agreement with the Crown including amongst his conditions an Earldom and some lands once held by his family.

Rumours rapidly spread that he had been poisoned by the English republican forces of Oliver Cromwell (and in particular by O'Neill's recent former ally Coote) to remove a dangerous opponent.

[1] Among his many works, Turlough O'Carolan composed several tunes that referred to Irish leaders during the Confederate Wars, including Lord Inchiquin and Owen Roe.

It strongly endorses the idea that O'Neill was murdered and attributes his loss as the main reason for the catastrophic defeat to the English republicans under Oliver Cromwell, who occupied Ireland for the next decade, and deprived many Catholic leaders of their lands in the 1652 Act of Settlement.