Chimmo Branson / Midshipman
Ballard Berkeley / Engineer Commander
Hubert Gregg / Pilot
James Donald / Doc
Michael Whittaker / Sub
Kenneth Carten / Sub-Lieutenant R.N.V.R.
John Varley / Secco
Caven Watson / Brodie
Geoffrey Hibbert / Joey Mackeridge
Richard Attenborough / Young Stoker
Frederick Piper / Edgecombe
Lionel Grose / Reynolds
Leslie Dwyer / Parkinson
Charles Russell / Fisher
John Singer / Moran
Robert Moreton / Coombe
John Boxer / Hollett
Kenneth Evans / Posty
Johnnie Schofield / Coxswain
Franklyn Bennett / Cmdr. Spencer
Charles Compton / No. 1. 'Tremoyne'
Walter Fitzgerald / Col. Lumsden
Gerald Case / Jasper
Daniel Massey / Bobby Kinross
Ann Stephens / Lavinia Kinross
Kathleen Harrison / Mrs. Blake
Dora Gregory / Mrs. Lemmon
Penelope Dudley-Ward / Maureen
Barbara Waring / Mrs. Macadoo
Eileen Peel / Mrs. Farrell
Lesley Osmond / Nell Fosdick
Josie Welford / Emily
Kay Young / Barmaid
Trixy Scales / Mona Duke
George Carney / Mr. Blake
Wally Patch / Uncle Fred
Michael Anderson / Albert Fosdick
Jill Stephens / May Blake
Everley Gregg / Nurse
Roddy Hughes / Photographer
Norman Pierce / Mr. Satterthwaite
Juliet Mills / Freda's Baby
Neville Chamberlain / Self (voice) (archive sound)
John Brabourne / Soldier in the Dunkirk Sequence
Robin Burns / Survivor Crewman
Jeremy Hawk / Train Passenger
Adolf Hitler / Self (archive footage)
Leslie Howard / Narrator (voice)
Al Millen / Rescued sailor

John Leyton / Willie 'Tunnel King'
Angus Lennie / Ives 'The Mole'
Nigel Stock / Cavendish 'The Surveyor'
Robert Graf / Werner 'The Ferret'
Jud Taylor / Goff
Hans Reiser / Herr Kuhn
Harry Riebauer / Strachwitz
William Russell / Sorren
Robert Freitag / Capt. Posen
Ulrich Beiger / Preissen
George Mikell / Lt. Dietrich
Lawrence Montaigne / Haynes ('Diversions')
Robert Desmond / Griffith 'Tailor'
Til Kiwe / Frick
Heinz Weiss / Kramer
Tom Adams / Dai Nimmo ('Diversions')
Karl-Otto Alberty / S.S. Officer Steinach
Arthur Atkinson / British Officer Charlie (uncredited)