State Secret is a 1950 British drama thriller film directed by Sidney Gilliat and starring Douglas Fairbanks Jr., Jack Hawkins, Glynis Johns, Olga Lowe and Herbert Lom.

[3]John Marlowe is an American surgeon visiting England when he is invited to Vosnia (a fictitious East-European country) to receive the "Kepler Gold Medal" for his contributions to medical science, and, coincidentally, to demonstrate his new techniques on a patient.

Galcon arranges a "shooting accident" for Marlowe, but as he is about to walk outside to his fate, the substitute for dictator Niva makes a live speech on the radio, and shots are heard.

He decided it would make a "chase thriller" in the style of films he had written for Alfred Hitchcock and Carol Reed, notably The Lady Vanishes and Night Train to Munich.

[5] The fictitious "Vosnian" language was constructed for the film by a linguistics expert, combining Latin and Slavic based elements.

"[7] In July it was announced that another Hollywood star would play the female lead but by August, actress Glynis Johns got the role.

[5] In The New York Times, Bosley Crowther wrote, "... this picture is just about as lively as they come, and under Mr. Gilliat's direction, it moves like an auto gaining speed ...

And it also has the advantage of good performance by all concerned—by Mr. Fairbanks as the kidnapped surgeon, looking a little like Eugene O'Neill; by Miss Johns, very saucy and explosive, as the music-hall girl; by Jack Hawkins as the Vosnian premier [sic], with an Oxford accent and a Nazi attitude; by Herbert Lom as the Balkan shyster and any number of others in small roles.