"Just like Magritte's picture of a pipe, a potato is not just a potato," says Romain Cools, head of Belgapom, the Belgian potato trade body. "You cannot compare bintje with other varieties."

The bintje, as you probably already know, is the world's most widely grown potato cultivar. But size, as it turns out, does indeed matter and demand for the smaller shorter bintje is... well, down.