Margaret Rutherford
Grand Duchess Gloriana XIII
Ron Moody
Prime Minister Rupert Mountjoy
Bernard Cribbins
Vincent Mountjoy
David Kossoff
Professor Kokintz
Terry-Thomas
Maurice Spender
June Ritchie
Cynthia
John Le Mesurier
British Delegate
John Phillips
Bracewell - U.S. Delegate
Eric Barker
M.I.5. Man
Roddy McMillan
Benter
Tom Aldredge
Wendover
Michael Trubshawe
British Aide
Peter Sallis
Russian Delegate
Clive Dunn
Bandleader
Hugh Lloyd
Plumber
Graham Stark
Standard Bearer
Mario Fabrizi
Mario - the Valet
Jan Conrad
Russian Aide
John Bluthal
Von Neidel (as John Bluthall)
Archie Duncan
U.S.A.F. General
Guy Deghy
Russian Scientist
Richard Marner
Russian Air Force General
Allan Cuthbertson
Member of Whitehall Conference
Robin Bailey
Member of Whitehall Conference
Gerald Andersen
Member of Whitehall Conference
Gordon Phillott
Civil Sergeant
John Wood
Countryman
George Chisholm
Wine Waiter
Rosemary Scott
Launching Lady
Vincent Ball
Pilot
Frank Duncan
News Announcer
Ed Bishop
American Astronaut (as Edward Bishop)
Bill Edwards
American Astronaut
Laurence Herder
Russian Astronaut
Harvey Hall
Russian Astronaut
Frankie Howerd
Self
Beverly Bennett
(Uncredited)
Paul Beradi
Ukraine Delegate (Uncredited)
Ernest Blyth
Dignatory at Ship Launching (Uncredited)
Michael Caspi
(Uncredited)
Paul Cole
(Uncredited)
Douglas Cooper
Fenwickian (Uncredited)
Larry Cross
(Uncredited)
Victor Croxford
Valet (Uncredited)
George Curtis
Councillor (Uncredited)
Stringer Davis
1st Councillor (Uncredited)
Charles Dyer
Bit Part (Uncredited)
Lucy Griffiths
Lady-in-Waiting (Uncredited)
Sandra Hampton
April (Uncredited)
Robert Haynes
(Uncredited)
Murray Kash
(Uncredited)
Frederick Kelsey
Fenwickian (Uncredited)
Bruce Lacey
Bandleader (Uncredited)
Anthony Lang
Councillor (Uncredited)
Frank Lieberman
American Civilian (Uncredited)
Martin Lyder
Fenwickian (Uncredited)
Jack Mandeville
Representative at United Nations (Uncredited)
Coral Morphew
Peasant Girl (Uncredited)
Carolyn Pertwee
June (Uncredited)
Stuart Saunders
Sergeant (Uncredited)
Kevin Scott
American Journalist (Uncredited)
George Spence
Man in Market (Uncredited)
Reg Thomason
Opposition MP (Uncredited)
Fred Wood
Bird Seller (Uncredited)