In his private character Shane O'Neill was a brutal, uneducated savage.
Hugh then appealed to Shane O'Neill, who invaded Tyrconnel at the head of a large army in 1557, desiring to make himself supreme throughout Ulster, and encamped on the shore of Lough Swilly.
Calvagh was then recognized by the English government as lord of Tyrconnel; but in 1561 he and his wife were captured by Shane O'Neill in the monastery of Kildonnell.
His wife, Catherine Maclean, who had previously been the wife of the earl of Argyll, was kept by Shane O'Neill as his mistress and bore him several children, though grossly ill-treated by her savage captor; Calvagh himself was subjected to atrocious torture"during the three years that he remained O'Neill's prisoner.
The rest of the earl's life was mainly occupied by endeavours to maintain his influence, and by an undying feud with his son Shane (John), arising out of his transaction with Henry VIII.