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)