|A.K.A.||Maria Seymour-Conway, Maria Emilia Fagnani|
|Birth||August 24, 1771 (London)|
|Death||March 2, 1856 (Paris)|
Maria Emilia Fagnani (24 August 1771 – 2 March 1856) was the Marchioness of Hertford.
Maria was illegitimate. Born in the 1770s, most likely, she was the daughter of Costanza Brusati, the Italian Marchesa Fagnani, and of either -
- William Douglas, 4th Duke of Queensberry (1724–1810), who was famously detested by Robert Burns.
- George Selwyn (1719–1791), a prominent Tory and lover of Grace Elliott. He was also a member of the Satanic Hellfire Club.
- George Selwyn's butler.
Both Queensberry and Selwyn believed themselves to be her father and left her very large legacies.
On 18 May 1798, Maria married Francis Seymour-Conway, Earl of Yarmouth (1777–1842), the son of the 2nd Marquess of Hertford and Isabella Ingram-Shepheard. The Marchioness was the daughter of the Viscount Irvine, and the mistress of the Prince of Wales.
By 1802 they were estranged, and she lived in Paris for the rest of her life.
- Lady Francis Maria Seymour-Conway (d. 1822)
- Captain Richard Seymour-Conway, 4th Marquess of Hertford (1800–1870)
- Lord Henry Seymour-Conway (1805–1859)
When George III of the United Kingdom was insane, he announced that he was going to take Lady Yarmouth as his mistress.
The Marquess inherited his title in 1822. He died in 1842. The dowager Marchioness died in 1856 in Paris.
William Makepeace Thackery parodied her husband as the Marquess of Steyne in his masterpiece, Vanity Fair.