Benedict Cumberbatch as Alan Turing

Keira Knightley as Joan Clarke

Matthew Goode as Hugh Alexander

Rory Kinnear as Detective Robert Nock

Allen Leech as John Cairncross

Matthew Beard as Peter Hilton

Charles Dance as Commander Denniston

Mark Strong as Stewart Menzies

James Northcote as Jack Good

Tom Goodman-Hill as Sergeant Staehl

Steven Waddington as Superintendent Smith

Ilan Goodman as Keith Furman

Jack Tarlton as Charles Richards

Alex Lawther as Young Alan Turing

Jack Bannon as Christopher Morcom

Tuppence Middleton as Helen

Dominic Charman as Sherborne Student 1

James G. Nunn as Sherborne Student 2

Charlie Manton as Sherborne Student 3

David Charkham as Joan's Father

Victoria Wicks as Joan's Mother

Andrew Havill as Teacher

Laurence Kennedy as Headmaster

Tim van Eyken as MI6 Agent

Will Bowden as Military Policeman

Miranda Bell as Margaret

Tim Steed as Electrical Assistant

Hayley Joanne Bacon as Woman in Crowd (uncredited)

Nicholas Blatt as Ministry Man (uncredited)

Ancuta Breaban as Wren (uncredited)

Alex Corbet Burcher as Dancer (uncredited)

Grace Calder as Assistant Wren (uncredited)

Richard Campbell as Crossword Man in Pub (uncredited)

Daniel Chapple as MI6 Agent (uncredited)

Lisa Colquhoun as Joan Clarke's Friend (uncredited)

Alexander Cooper as Bletchley Park Agent (uncredited)

Leigh Dent as Passerby (uncredited)

Sam Exley as Military Policeman 3 (uncredited)

Dennis Good as Civilian (uncredited)

Debra Leigh-Taylor as Evacuee (uncredited)

Stuart Matthews as Bletchley Park Operative (uncredited)

Joseph Oliveira as MI6 Agent (uncredited)

David G. Robinson as Police Sergeant White (uncredited)

Mark Underwood as Crossword Man (uncredited)

Nicola-Jayne Wells as First Aid Nurse (uncredited)

Josh Wichard as German Pilot (uncredited)

Joshua Wichard as German Spy Plane Pilot (uncredited)