Suppose you have every reason to believe that you own a Bentley, since you have had it in your possession for many years, and you parked it that morning at its usual spot. However, it has just been destroyed by a bomb, so that you own no Bentley, despite your well justified belief that you do. As you sit in a cafe having your morning latte, you muse that someone in that cafe owns a Bentley (since after all you do). And it turns out you are right, but only because the other person in the cafe, the barista, owns a Bentley, which you have no reason to suspect. So you here have a well justified true belief that is not knowledge.