Ed Stoppard

Alan Turing

Henry Goodman

Franz Greenbaum

Paul McGann

Himself - Narrator (voice)

Asa Briggs

Himself - Codebreaker, Bletchley Park

Jean Valentine

Herself - WRNS and Bombe Operator, Bletchley Park

David Leavitt

Himself - Alan Turing's Biographer

Rolf Noskwith

Himself - Codebreaker, Bletchley Park

Dermot Turing

Himself - Alan Turing's Nephew

Christopher Morcom

Himself - Christopher Morcom's Nephew (as Christopher Morcom QC)

Ian Stewart

Himself - University of Warwick (as Professor Ian Stewart)