3. Emilia Fox
Part of the talented Fox dynasty of actors, Emilia Fox is well known for her role as Dr. Nikki Alexander in BBC's Silent Witness, having appeared since series eight, with the show delving into its seventeenth next year. The character of Nikki portrays an irrepressible curiosity and undeniable intelligence, something which Emilia Fox herself maintains, being an Oxford University graduate. Emilia Fox could add charm to Ripper Street, with her vast catalogue of acting credits, she could play almost any role required. I could see her playing either an unattainable, upper-class love interest for one of the three heroes, she certainly has the grace to pull off an alluring figure, either as a genuine attraction or a manipulative temptress controlling an investigation. She could even portray a killer, having shown her ability in ITV's 2007 mini-series Fallen Angel where she played psychotic killer Rosie Byfield.