Not being in holy orders he was, by the terms of suppression, relieved of his first vows, and soon afterwards married Dorothea, daughter of George J. Griffith Phillips, esq., of Curaegwillinag, Carmarthenshire.
While in Dublin (1811) he published his work "Ireland since the Union" which led to a prosecution on the part of the Government for libel, resulting in a verdict of £5000 damages.
He escaped to Paris where he spent the remaining years of his life in comparative poverty as a professor at the Scots College, dying on 4 January 1829, aged 79.
Plowden answered by a Posthumous Preface giving an account of his communications with Henry Addington, 1st Viscount Sidmouth, and also by a Historical Letter to Sir Richard Musgrave.
His Historical Letters to Sir John Coxe Hippisley (1815) contained matter connected with the question of Catholic emancipation.