According to the wife of former British Union of Fascists leader Oswald Mosley, Diana Mitford, who knew both Queen Elizabeth and the Duchess of Windsor but was only friendly with the latter, the Queen's antipathy toward her sister-in-law may have resulted from jealousy. Lady Mosley wrote to her sister, the Duchess of Devonshire, after the death of the Duke of Windsor, "probably the theory of their Windsors' contemporaries that Cake Mitford nickname for the Queen Mother was rather in love with him Duke (as a girl) & took second best, may account for much."