Life
?1606-1644; son of Brian MacMahon Oge MacMahon, lord of Dartree, Co. Monaghan with a dg. of Hugh O"Neill; joined Northern conspiracy, 1641; planned assault on Dublin Castle, betrayed and arrested; escaped from Tower of London, 1644; retaken, tried and executed. ODNB
ODNB: [...] induced to join the northern conspiracy, and was appointed with Connor, lord Maguire [q. v.], and others to undertake the capture of Dublin Castle. Among his acquaintances was one Owen O’Connolly, a man of some standing, at one time in the employment of Sir John Qotworthy, and though a protectant by profession, supposed to be secretly attached to the Roman catholic religion, and not averse to the plans of the conspirators. This man MacMahon invited to visit him on business of great importance at his house at Connagh a day or two before the date assigned for the outbreak of the rebellion, but being6unable to wait for him he proceeded to Oxmantown, near Dublin, at which place he was to be joined by the other conspirators. Thither O’Connolly came on Friday evening, 22 Oct., and was by MacMahon made acquainted with the details of the plot. But alarmed by what he had heard, and eluding MacMahon’s vigilance, O’Connolly revealed the secret to the lord justices, Sir William Parsons and Sir John Borlase and they, taking instant measures, arrested MacMahon, after some show of resistance, early on the following morning. Being brought before the council he at first [denied] all knowledge of the conspiracy, but eventually “confessed enough to destroy himself and impeach some others.” After several months’ confinement in Dublin, he was by order of the parliament sent to England, with Lord Maguire and Colonel Read, in June 1642, and committed to the Tower. He was examined by the judges of the king's bench, but owing to the difficulty of obtaining witnesses from Ireland he was recommitted to the Tower, where he remained till 17 Aug. 1644, when, with the assistance of two priests attached to the Spanish embassy, he and his fellow-prisoner, Lord Maguire, managed to escape. A reward of £100. was offered for his apprehension, and on 19 Sept. he and Lord Maguire were discovered accidentally by a servant of Sir John Clotworthy's in a constable's house in Drury Lane. He was at once recommitted to the Tower, and a true bill having been found against him, he was on 18 Nov. arraigned before the court of king’s bench. The prosecution was conducted by Prynne, and having been found guilty of high treason, he was executed at Tyburn on the 22nd, “and being asked if he desired any to pray for him answered, none but Roman catholics.” (Cites Carte’s Life of Ormonde, Shirley’s History of Monaghan, Gilbert’s Aphorismical Discovery, Cobbett"s State Trials, and Irish genealogies [Harl. MS 1425ff,178, 192.] Available online; accessed 03.11.2023.)