Ah, the powers of reflex.
Orwell, talking of how the world had far from shrunk in his day, wrote of how it used to be that the only country in Europe you needed a passport for was Russia. Customs, of course, would be plausible, but not checking papers for whether they were in order. (Since they are not in fact going to a Russia-equivalent at this point. Probably nowhere on their tour, actually.)
One reason why I recommend massive reading of primary source is to knock your block off, so that you know the grave danger of automatically reach for what is familiar and slapping it down in the middle of a pseudo-medieval or pseudo-Victorian setting. But it doesn't mean that it cures you forever.