Career
He sat in the Irish House of Commons for Kinsale from 1692 to 1699, for Dublin University from 1703 to 1713 and then again for Kinsale from 1713 to his death. In 1702 Southwell succeeded his father as Principal Secretary of State (Ireland) and was appointed to the Privy Council of Ireland the same year. He sat in the House of Commons of England and the House of Commons of Great Britain between 1702 and 1715 as Member of Parliament for Rye, Tregony and Preston.