There are conflicting reports as to the true inspiration for the film, lawyer Jules François Clermont or actor Claude Dauphin.
[1] In September 2011, The Daily Telegraph published an article noting that writer and actor Claude Dauphin had collaborated with Hitchcock to recount his own experiences of operating an underground radio station in Nazi occupied France.
He reminisces about a very unpleasant Vichy official, the Chef de la Sûreté, whom he knew when he was part of the Resistance on the island of Madagascar during the Second World War.
Paul Clarus pretended to be loyal to the Vichy official, while he simultaneously worked as the head of the Resistance movement.
He ran an illegal pro-Resistance radio station "Madagascar Libre", and helped arrange numerous boats to take loyal Frenchmen out of the island to safety.