Margaret Rutherford as Grand Duchess Gloriana XIII

Ron Moody as Prime Minister Rupert Mountjoy

Bernard Cribbins as Vincent Mountjoy

David Kossoff as Professor Kokintz

Terry-Thomas as Maurice Spender

June Ritchie as Cynthia

John Le Mesurier as British Delegate

John Phillips as Bracewell - U.S. Delegate

Eric Barker as M.I.5. Man

Roddy McMillan as Benter

Tom Aldredge as Wendover

Michael Trubshawe as British Aide

Peter Sallis as Russian Delegate

Clive Dunn as Bandleader

Hugh Lloyd as Plumber

Graham Stark as Standard Bearer

Mario Fabrizi as Mario - the Valet

Jan Conrad as Russian Aide

John Bluthal as Von Neidel (as John Bluthall)

Archie Duncan as U.S.A.F. General

Guy Deghy as Russian Scientist

Richard Marner as Russian Air Force General

Allan Cuthbertson as Member of Whitehall Conference

Robin Bailey as Member of Whitehall Conference

Gerald Andersen as Member of Whitehall Conference

Gordon Phillott as Civil Sergeant

John Wood as Countryman

George Chisholm as Wine Waiter

Rosemary Scott as Launching Lady

Vincent Ball as Pilot

Frank Duncan as News Announcer

Ed Bishop as American Astronaut (as Edward Bishop)

Bill Edwards as American Astronaut

Laurence Herder as Russian Astronaut

Harvey Hall as Russian Astronaut

Frankie Howerd as Self

Beverly Bennett as (Uncredited)

Paul Beradi as Ukraine Delegate (Uncredited)

Ernest Blyth as Dignatory at Ship Launching (Uncredited)

Michael Caspi as (Uncredited)

Paul Cole as (Uncredited)

Douglas Cooper as Fenwickian (Uncredited)

Larry Cross as (Uncredited)

Victor Croxford as Valet (Uncredited)

George Curtis as Councillor (Uncredited)

Stringer Davis as 1st Councillor (Uncredited)

Charles Dyer as Bit Part (Uncredited)

Lucy Griffiths as Lady-in-Waiting (Uncredited)

Sandra Hampton as April (Uncredited)

Robert Haynes as (Uncredited)

Murray Kash as (Uncredited)

Frederick Kelsey as Fenwickian (Uncredited)

Bruce Lacey as Bandleader (Uncredited)

Anthony Lang as Councillor (Uncredited)

Frank Lieberman as American Civilian (Uncredited)

Martin Lyder as Fenwickian (Uncredited)

Jack Mandeville as Representative at United Nations (Uncredited)

Coral Morphew as Peasant Girl (Uncredited)

Carolyn Pertwee as June (Uncredited)

Stuart Saunders as Sergeant (Uncredited)

Kevin Scott as American Journalist (Uncredited)

George Spence as Man in Market (Uncredited)

Reg Thomason as Opposition MP (Uncredited)

Fred Wood as Bird Seller (Uncredited)