The title refers to the fact that Jerusalem (words by William Blake, music by Hubert Parry) is the anthem of the Womens' Institute, to which Miss Bunyon, Miss Thimble and Mrs. Fortescue (the "daughters") belong.
Vera Thimble is listening to the BBC docudrama "The Archers" when her murderer enters the room, based on the the theme song playing on the radio.