There is an Englishmen, Irishmen and a Frenchman in the desert. They come across a lamp and rub it three times. A genie comes out.
"I shall grant each of you but a single wish" he intones.
"I want to go to back Ireland," pipes up the Irishman, "with a mug of ale that can never empty."
"Done!" said the genie, and with a puff of smoke, the the Irishman lives the rest of his days as a hero in Ireland.
Next came the Frenchman. "Genie," he said in a really thick French accent, "I am sick of these foreigners coming into my land. I want a great wall around France to let no one in or out, and I want to be inside when it happens."
"Done!" said the genie, and with a puff of snoke, the Frenchman returned to Paris and France was protected by the massive wall.
Finally came the Englishman. "Tell me more about this wall" he asked.
"Well, it is 2 kilometres high, surrounds the entire border of France and nothing can get in or out" replied the genie.
The Englishman thinks for a bit. "Fill it with water."