Sam Rockwell as Inspector Stoppard[1] Saoirse Ronan as Constable Stalker[1] Adrien Brody as Leo Köpernick[2] Ruth Wilson as Petula Spencer[3] Reece Shearsmith as John Woolf[4] Harris Dickinson as Richard Attenborough[5] David Oyelowo as Mervyn Cocker-Norris[1] Charlie Cooper as Dennis the Usher[5] Shirley Henderson as the Dame[5] Pippa Bennett-Warner as Ann Saville[6] Pearl Chanda as Sheila Sim[5] Paul Chahidi as Fellowes[5] Sian Clifford as Edana Romney[5] Jacob Fortune-Lloyd as Gio[5] Lucian Msamati as Max Mallowan[7] Tim Key as Commissioner Harrold Scott[8]