Seymour was returned unopposed for Totnes in 1763 and, through his half-brother Lord Sandwich, attached himself to Grenville’s Administration and was appointed to the bedchamber. On Grenville’s dismissal he resigned his place and went into opposition. A frequent speaker in the House, he spoke, 14 Jan. 1766, on Grenville’s motion for enforcing the Stamp Act and took a leading part in the opposition to its repeal. On 13 July 1767, when Rockingham was trying to form an Administration from all the Opposition parties, Seymour wrote to Grenville:
I have just been informed of the state ... of public affairs, and as I have never had but one view or object, which is that of accompanying you through every scene of fortune as far as I can carry myself, I own I wish much to know from yourself if this arrangement now forming is agreeable to your sentiments ... Should your wishes to serve the public engage you again into the field of business and employment, I own I should prefer the setting at any Board at which you shall preside beyond any other inducement, provided this shall be your inclination as it is mine.
Soon after his election he had set about consolidating his interest at Totnes, and had applied to Grenville for the disposal of Government patronage in the borough. ‘I hope I need not add’, wrote Sandwich to Grenville on 4 Oct. 1763,
From 1768 to 1770 Seymour was one of the most active of the few followers who remained to Grenville. For the Parliament of 1768, 138 speeches by him are reported in Cavendish’s ‘Debates’, and Sandwich described him in 1770 as ‘one of the most violent politicians in England’. He remained in opposition after February 1771 when the majority of Grenville’s friends went over to the court, and said in a speech in the House on 27 Mar.:
He was elected for Evesham in 1774 after a contest, and continued in opposition after the American war broke out. But his attendance in the House seems to have been less frequent, and between 1774 and 1776 only two speeches are recorded. In 1777 he settled at Prunay in France, and in 1778 applied for legal domicile. He became the lover of Madame du Barry, separated from his wife, and did not return to England until driven out by the Revolution in 1792.
He died 14 Apr. 1807.
