This is her article in thepeerage that shows just how pervasive the lack of vital statistics record keeping was, "Mary Fawkener F, #4686, d. 4 February 1860
Mary Fawkener was the daughter of William Augustus Fawkener. She married Horatio Walpole, 3rd Earl of Orford, son of Horatio Walpole, 2nd Earl of Orford and Sophia Churchill, on 23 July 1812. She died on 4 February 1860.
Her married name became Walpole. As a result of her marriage, Mary Fawkener was styled as Countess of Orford on 15 June 1822.
Children of Mary Fawkener and Horatio Walpole, 3rd Earl of Orford
Lady Dorothy Fanny Walpole+ d. 24 Mar 1913
Lady Rachel Katherine Walpole+ d. 21 Jun 1854
Horatio William Walpole, 4th Earl of Orford+ b. 18 Apr 1813, d. 7 Dec 1894
Hon. Henry Walpole b. 1 May 1818, d. 6 Nov 1876
Commander Hon. Frederick Walpole+ b. 18 Sep 1822, d. 1 Apr 1876."
From eBay. This is one of several prints of beauties in Queen Victoria's court released in 1849. The original was prepared over a decade earlier based on her coiffure.