Steven Mackintosh
Himself - Narrator
Brian Deacon
Gordon Welchman (voice)
Rosamund Welchman
Herself - Gordon Welchman's Daughter
W. Gordon Welchman
Himself - Ex-Head of Hut 6, Bletchley Park (1939-1941) (archive footage)
Sinclair McKay
Himself - Author, 'The Secret Life of Bletchley Park'
Jimmy Thirsk
Himself - Veteran, Hut 6
Asa Briggs
Himself - Veteran, Hut 6
Jane Fawcett
Herself - Veteran, Hut 6
Tony Comer
Himself - GCHQ Historian and Former Analyst
John Naughton
Himself - Vice President, Wolfson College, Cambridge (as Prof John Naughton)
John Scarlett
Himself - Chairman, Bletchley Park Trust, and Former Chief, MI6 (as Sir John Scarlett KCMG OBE)
Jennifer Welchman
Herself - Gordon Welchman's Granddaughter
Robert R. Everett
Himself - Former President, The MITRE Corporation
Eric Ellingson
Himself - Gordon Welchman's Colleague
Larry Hill
Himself - Gordon Welchman's Colleague