King Arthur went off to war.

He of course made Queen Guinevere wear a Chasity belt. Because he wasn't sure he wasn't coming back, he gave a copy of the key to his most trusted knight, Sir Lancelot. As the king and his army were just going over the top of the first rise leading away from Camelot, Sir Lancelot came riding up as fast as his trusted mount could gallop. "King Arthur, King Arthur! You gave me the wrong key! You gave me the wrong key!"