Sam Rockwell as Inspector Stoppard

Saoirse Ronan as Constable Stalker

Adrien Brody as Leo Köpernick

Ruth Wilson as Petula Spencer

Reece Shearsmith as John Woolf

Harris Dickinson as Richard Attenborough

Charlie Cooper as Dennis Corrigan

David Oyelowo as Mervyn Cocker-Norris

Kieran Hodgson as Harley the Motorcycle Messenger

Pearl Chanda as Sheila Sim

Gregory Cox as Major Metcalf

Maggie McCarthy as Mrs. Boyle

Oliver Jackson as Trumpet

Tomi Ogbaro as Double Bass

Sian Clifford as Edana Romney

Jacob Fortune-Lloyd as Gio

Ania Marson as Mother

Tim Key as Commissioner Harrold Scott

Philip Desmeules as Pierre

Laura Morgan as Joyce

Pippa Bennett-Warner as Ann Saville

Angus Wright as Sgt Bakewell

Shirley Henderson as Agatha Christie

Paul Chahidi as Fellowes

Lucian Msamati as Max Mallowan

Tolu Ogunmefun as Mr. Lyon