[3] Styled Earl Jermyn after his father was raised to a marquessate in 1826, he became a member of Parliament as one of two representatives for Bury St Edmunds the same year.

[2][4] In 1841 he was sworn of the Privy Council[5] and appointed Treasurer of the Household in the Tory administration of Sir Robert Peel,[6] an office he retained until the government fell in 1846.

[7] He continued to represent Bury St Edmunds in Parliament until 1859, when he succeeded his father in the marquessate and entered the House of Lords.

They had four sons and three daughters: Countess Jermyn died at 47 Eaton Place, London, on 20 April 1848, from smallpox, in a childbed, aged 39.

Lord Bristol remained a widower until his death at Ickworth House, Suffolk, on 30 October 1864, aged 64.