Steven Mackintosh
Himself - Narrator
Brian Deacon
Gordon Welchman (voice)
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Rosamund Welchman
Herself - Gordon Welchman's Daughter
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W. Gordon Welchman
Himself - Ex-Head of Hut 6, Bletchley Park (1939-1941) (archive footage)
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Sinclair McKay
Himself - Author, 'The Secret Life of Bletchley Park'
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Jimmy Thirsk
Himself - Veteran, Hut 6
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Asa Briggs
Himself - Veteran, Hut 6
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Jane Fawcett
Herself - Veteran, Hut 6
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Tony Comer
Himself - GCHQ Historian and Former Analyst
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John Naughton
Himself - Vice President, Wolfson College, Cambridge (as Prof John Naughton)