The 9th baron took an active part in talks between leading Catholic peers and the King's representatives in the 1620s. He was given new lands in several counties, even as some in government were concerned about the number of Catholic clergy within his extended family. When a rebellion began in Ulster in 1641, Dunsany attended a session of the Irish Parliament to address the matter, and offered to intercede; he later became further entangled in the debates among leading Irish families. While eventually agreeing to support the rebellion, he also sheltered Protestant families, helping some reach Dublin. He was confined in Dublin Castle from March 1642 to September 1643.[1][2]
In 1648, Dunsany took the Catholic Confederation oath of loyalty. His lands were seized by Oliver Cromwell's forces in the 1650s, and he lived in deprived circumstances for many years thereafter. After the Restoration in 1660, it was indicated in the King's name that he should receive his lands back, but a later court ruling went against him, albeit he eventually secured a provision for a son to inherit all rights back. In 1665 he was restored to the title of Dunsany Castle and one-third of his former lands, with the rest to be restored later - this did not fully happen.[1][2]