Granville served as British ambassador to Russia (1804-1807) and France (1824-1828, 1830-1835, 1835-1841).
The Earl and Countess Granville threw events that were often the toast of Parisian society while he was a British diplomat.
Lord Granville, prior to marrying Lady Harriet Cavendish, was the lover of Lady Harriet's maternal aunt, Henrietta Frances Ponsonby, Countess of Bessborough, nee Lady Henrietta Frances Spencer, with whom he fathered two illegitimate children:
Harriet Stewart and George Stewart.
He was created Viscount Granville in 1815 and Earl Granville in 1833.
He had one son by Lady Harriet: Granville Leveson-Gower, 2nd Earl Granville. He also had two daughters by Lady Harriet:
Susan and Georgiana, who both received the title of Lady after he became an Earl.
Susan married Baron Rivers.
Georgiana married Alexander Fullerton. She was a biographer, novelist and great philanthopist.