Powlett, Isabella, Countess of Egmont -1794)
Isabella Powlett was the only daughter and heir of Lord Nassau Powlett, third son of Charles, 2nd Duke of Bolton, the only child by his third wife Lady Henrietta Crofts, daughter of James Duke of Monmouth, and Eleanor Needham. She married, 4 June 1765, John James Perceval (1738-1822), who succeeded his father as 3rd Earl of Egmont, in 1772. She died 8 September 1821. They had an only son, John, who succeeded as 4th Earl of Egmont.