Seymour-Conway was returned for two Parliamentary seats in 1771:
Lisburn, in the
Parliament of Ireland, and the family borough of
Orford in the
British House of Commons. In 1773, he became a
major in the
3rd Irish Horse. and became captain of a company in the regiment on 30 January 1776. He gave up his seat at Lisburn that year, but continued to sit for Orford. He served as an
aide-de-camp to
Sir Henry Clinton in America from 1780 to 1781, but resigned his commission in 1782. On 2 December 1803, he was appointed Lieutenant-Colonel Commandant of the 2nd Battalion, Carmarthenshire Volunteers. He resigned that command on 6 January 1808. During the
1807 election, Seymour was returned both for Orford and
Carmarthenshire, choosing to sit for the latter, which he represented until 1820. On 1 July 1807, Seymour, who owned a house in
Portland Place, was sworn a
Justice of the Peace for
Middlesex. He took an active role in civic affairs in London, and was for some time Director of the Poor for his parish of
St Marylebone. This included a particular interest in the care and treatment of the insane, culminating in his appointment in 1827 to the commission superintending the building of
Hanwell Asylum and as a
Metropolitan Commissioner in Lunacy in 1828. However, he was now approaching the end of his life and played little active role as a Lunatic Commissioner. In 1829, Seymour funded the building of the north transept and a vicarage for Taliaris Chapel. ==Personal life==