- Margaret Lockwood
- Frances Gray
- Dane Clark
- Bill Casey
- Marius Goring
- Commandant Anton Razinski
- Naunton Wayne
- Mr. Hedgerley
- Wilfrid Hyde-White
- Mr. Luke - British consul
- Eugene Deckers
- Alf - the 'contact'
- Olaf Pooley
- Detective-Interrogator
- Gladys Henson
- Snack Bar Attendant
- Paul Hardtmuth
- Priest
- Michael Hordern
- Owens - Lab Director
- George Benson
- Sandwich Stand Customer
- Eric Pohlmann
- Joe - the bartender
- John Horsley
- Customs Officer
- Patric Doonan
- Customs Man
- Joan Haythorne
- Judy
- Jill Balcon
- Wardress
- Hyma Beckley
- Cafe Mimosa Patron
- John Boxer
- Police Sergeant at Customs Cafe
- Daniel Brown
- Train Passenger
- Ernest Butcher
- Tom - lab assistant
- Robert Cawdron
- Soldier at Barrier During Fire
- Anton Diffring
- Officer At Station Checkpoint.
- Toni Frost
- Stewardess
- John Gabriel
- Night Field Telephone Officer
- Charles Hammond
- Train Passenger in Platform Line-up
- Philo Hauser
- Waiter
- John G. Heller
- Soldier at Station Check Point
- Noel Johnson
- Frank Conway
- Sam Kydd
- Customs Man
- Richard Marner
- Soldier on Train
- Louis Matto
- Cafe Minosa Waiter
- Anthony Newley
- Operator
- Michael Rittermann
- The 'Tail'
- Lance Secretan
- Alan
- Dinah Sheridan
- Train passenger at checkpoint
- Ewen Solon
- Enemy Scientist
- Emile Stemmler
- Soldier at Station Checkpoint / Policeman at Frontier Station (uncredited)
- Robert Vossler
- Day Sentry at 1st Checkpoint
- John Wilder
- Customs Officer
- Billy Wilmot
- Café Mimosa Customer
