May Carleton

May Carleton is a wealthy widow and racehorse breeder who moves in the kind of aristocratic circles the Shelbys are trying to break into. Composed and sharp, she sizes up Tommy Shelby as both a business risk and something more, offering him entry to a world of titled money and legitimate respectability.

Riley plays her as cool rather than cold, a woman who has buried a husband and learned to negotiate from strength, which makes her scenes with Cillian Murphy crackle with two guarded people testing each other. She gives the show's class collision a human face instead of a lecture.