Clarissa Eden

Anne Clarissa Eden, Dowager Countess of Avon ("née" Spencer-Churchill; 28 June 1920 – 15 November 2021) was the widow of Anthony Eden, 1st Earl of Avon (1897–1977), who was British Prime Minister from 1955 to 1957. 
She married Eden in 1952, becoming Lady Eden in 1954 when he was made a Knight of the Garter, and then becoming Countess of Avon in 1961 on her husband's elevation to the peerage. She is also the niece of the prime minister Winston Churchill.
Her memoir, sub-titled "From Churchill to Eden", was published in 2007 under the name of Clarissa Eden.
Eden turned 100 in June 2020. She died on 15 November 2021, aged 101.