He owed the promotion to the goodwill of the Lord Deputy of Ireland, the Earl of Strafford, who hoped, rather cynically, to appease the Old Irish faction by appointing a few "token" judges of Gaelic origin.
[6] When the English Civil War broke out Donnellan was initially a Royalist; he had long been close to Ulick Burke, 5th Earl of Clanricarde in whom Charles I placed great trust.
[8] After the defeat of the Royalist cause, according to Henry Cromwell, Donnellan became a faithful supporter of the new regime, diligently persecuting his former allies.
James Butler, 1st Duke of Ormonde, the Lord Lieutenant of Ireland, who personally chose the new judges, had no strong objection to men of Gaelic background, but did normally require a record of loyalty to the Crown.
He was, for the time, a very old man, and his health quickly failed: well before his death the English Government was thinking of replacing him, but Ormonde requested that they wait till he was actually dead.