[1] Cromer's successor George Dowdall on 15 May 1544 appointed MacMahon instead as a suffragan bishop inter Hibernicos ("among the [Gaelic] Irish").
[3][4] When the Catholic Queen Mary I succeeded to the throne in 1553, papal supremacy was recognised and MacMahon received the temporalities of Ardagh.
[1] While Monahan says that Ardagh was vacant in the Church of Ireland after the accession of Elizabeth I,[1] others regard MacMahon as retaining his place in both hierarchies.
[5][6] A possibly forged papal bull, dated 1568, deprives MacMahon of his see for simony, non-residence, and neglect of the cathedral.
[1] A putative 1572 letter from Marshalsea from a former bishop "Malachy" of Ardagh, abjuring "papistical superstition" and promising loyalty to Elizabeth, may if genuine be from MacMahon.