River Cartright is a main character in the British spy thriller series, Slow Horses (based on the Slough House novels by Mick Herron).

Played by Jack Lowden, River Cartright is a promising MI5 agent who gets shifted off to Slough House after a very public mistake, Slough House being a site of drudgery for MI5 agents who have bungled their jobs but who haven’t been sacked.

River Cartright grew up in the kinship care of his grandfather, David Cartwright (Jonathan Pryce), a retired MI5 officer.