Lady Runcorn

In the short story The Double Clue, Lady Runcorn is one of the guests at the tea party hosted by Marcus Hardman where a valuable necklace was stolen.

Lady Runcorn belongs to one of the oldest families in England. Marcus Hardman describes her as "a middle-aged woman of considerable force of character who devotes most of her time to various charitable committees."

Lady Runcorn became a suspect because she returned to the room where the safe was in order to retrieve a handbag which she had left there.

Portrayals
Lady Runcorn is played by Charmian May in the film adaptation of The Double Clue in Series 3 of ITV's Agatha Christie's Poirot. In the adaptation, Lady Runcorn is given the maiden name "Beatrice Palmerston". This creates the suspicion that the cigarette case at the scene of crime could be hers as it had the initials "B.P." In fact, Poirot uses this fact to deflect suspicion from Vera Rossakoff. At the end of the episode, Poirot says the cigarette case is hers but she would always deny it. This was because she was short of money and had come to the party to meet Bernard Parker to try to sell the item.