(This joke is best told with the relevant accents. The stronger the better.)
The Russians train a spy to plant in Wales. They teach him all the Welsh dialects and Tom Jones lyrics and everything. He's to be dropped in a remote village on the West coast. All he knows about his contact is that the man's name is Jones.
So the Russian sub comes in late one night; the spy rows ashore in a black dinghy and buries it, and starts walking the few miles to the village, where he knows he will find his contact. Shortly after dawn, he's approaching the village and he sees a man approaching, coming the other way.
"Good morning," says the Welshman, cheerily.
"Good morning," says the Russian. "Excuse me, but is your name Jones?"
"Jones, yes, that's me, I'm Jones. Can I help you at all?"
The Russian hesitates, then says, quietly, "The sky is red at sunset."
"Ah, yes, I see," says the Welshman. "No, it's Jones the Spy you're looking for. I'll take you to him."