Deborah Vivien Cavendish , Duchess of Devonshire DCVO ( born Freeman-Mitford ; 31 March 1920 -- 24 September 2014 ) was an English writer , memoirist and socialite .
Deborah Vivien Cavendish , Duchess of Devonshire DCVO ( née Deborah Freeman-Mitford ; 31 March 1920 -- 24 September 2014 ) was a British writer and aristocrat .