Funny Thing Happened on the Way to London - S3-E5
Plot hole: When the driver of the car addresses Roberts (the real Roberts that is, not the double), Roberts reprimands him, telling him not to call him Baumann. It is safe to assume the guard was supposed to be speaking German, since he addressed Roberts by his German identity. That poses some interesting questions. Did Roberts speak English? In those days, most Germans did not even have a basic knowledge of the English language. Did he speak German? That would imply he has a good enough command of the German language to pass as a German. Roberts however isn't a spy like Hogan and his crew, but a pilot in the RAF.
Answer: It's a solitary cell. Steve McQueen, star of 'The Great Escape' is known as the 'Cooler King'.