[2] Jephson then lived in England, at Hampton Court, with William Gerard Hamilton.
[3] He published, in the Mercury newspaper, a series of articles in defence of the lord-lieutenant's administration which were afterwards collected and issued in book form under the title of The Bachelor, or Speculations of Jeoffry Wagstaffe.
[3] Jephson entered the Irish House of Commons in 1773 and sat for St Johnstown (County Longford) until 1776.
Among others, his tragedy Braganza was successfully performed at Drury Lane in 1775, The Conspiracy in 1796, Julia in 1797, The Law of Lombardy in 1779, and The Count of Narbonne at Covent Garden in 1781, adapted from Horace Walpole's The Castle of Otranto and The Campaign at the Smock Alley Theatre in 1784.
[4] In 1794 he published an heroic poem Roman Portraits, and The Confessions of Jacques Baptiste Couteau, a satire on the excesses of the French Revolution.