James Marsh Director Rachel Weisz Clare Crowhurst Actor Colin Firth Donald Crowhurst Actor David Thewlis Rodney Hallworth Actor Finn Elliot James Actor Andrew Buchan Ian Actor Jonathan Bailey Wheeler Actor Genevieve Gaunt Miss Teignmouth Actor Sebastian Armesto Nelson Messina Actor Ken Stott Mr. Best Actor Simon Chandler Sidney Rawle Actor Adrian Schiller Elliot Actor Kit Connor James Crowhurst Actor Sam Hoare Mr. Hughes Actor Oliver Maltman Dennis Herbstein Actor Graham Broadbent Producer Scott Z. Burns Producer, Screenwriter Peter Czernin Producer Nicolas Mauvernay Producer Jacques Perrin Producer Dan MacRae Executive Producer Diarmuid McKeown Executive Producer Jonny Persey Executive Producer Jóhann Jóhannsson Original Music Eric Gautier Cinematographer Jinx Godfrey Film Editing Joan Sobel Film Editing