Alan Turing

Benedict Cumberbatch

Joan Clarke

Keira Knightley

Hugh Alexander

Matthew Goode

John Cairncross

Allen Leech

Detective Robert Nock

Rory Kinnear

Stewart Menzies

Mark Strong

Peter Hilton

Matthew Beard

Commander Denniston

Charles Dance

Jack Good

James Northcote

Young Alan Turing

Alex Lawther

Sergeant Staehl

Tom Goodman Hill

Superintendent Smith

Steven Waddington

Charles Richards

Jack Tarlton

Keith Furman

Ilan Goodman

Helen

Tuppence Middleton

Sherborne Student 1

Dominic Charman

Christopher Morcom

Jack Bannon

Sherborne Student 3

Charlie Manton

Sherborne Student 1

Dominik Charman

Sherborne Student 2

James G. Nunn

Teacher

Andrew Havill

Headmaster

Laurence Kennedy

Joan's Father

David Charkham

MI6 Agent

Tim Van Eyken

Margaret

Miranda Bell

Joan's Mother

Victoria Wicks

Electrical Assistant

Tim Steed

Military Policeman

Viv Weatherall