The star, who plays lady's maid Anna Bates in the hit period drama, is set to appear in a dark new series about real life Victorian poisoner Mary Ann Cotton.

The killer was believed to have murdered three of her husbands for the insurance money, along with eleven of her thirteen children, and was hanged for her crimes in 1873.

Froggatt will play Cotton in Dark Angel, which will be filmed in Britain this summer (15).