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 being created an earl.
She is also the niece of Prime Minister Winston Churchill.
Her memoir, sub-titled From Churchill to Eden, was published in 2007 under the name of Clarissa Eden.
Since the death of Mary Wilson, Baroness Wilson of Rievaulx, on 6 June 2018, Lady Avon is the oldest living spouse of a British Prime Minister.