 In "The Duchess Assignment", the Duchess of Royston was based on the  distinguished British stage actress Edith Evans (I) (qv), best  known for her role as Lady Bracknell in the film version of  Oscar Wilde (qv)s _Importance of Being Earnest, The (1952)_ (qv).  This is reinforced by Ray Barrett (I) (qv)s marvelous voice for  the character, which understandably had the rest of the cast in  stitches at the recording session.