The Once and Future King Book 1, Chapter 23
The castle's inhabitants make their journey to London---a very dangerous one, because most of the way the roads are barely clear through the forest. London is very crowded, but Sir Ector owns a bit of land there, so they are able to find rooms to sleep in. However, the next morning Kay forgets his sword on the way to the tournament (where he hopes to joust) and sends Arthur back to their inn to get it. Arthur finds the inn locked up, so he walks around town trying to think of how to get a sword for Kay. He comes upon the famous sword in the stone and, not knowing what it is, tries to remove it. He can't move it, but he feels strange whenever he touches it: everything seems clearer and more beautiful and he can hear the voices of all the animals he knew throughout his childhood. "There is something in this place, " says Arthur curiously Book 1, Chapter 23, pg. 207 He hears each voice telling him how to take the sword-the owls, badgers, geese, etc. all contributing their strengths and knowledge-and then, suddenly, he removes the sword very easily.
Arthur brings the sword to Kay, who sees that it is not his sword, and, learning that it is the sword from the stone, he runs to Sir Ector-and tells him that he removed the sword! However, when Ector asks him directly whether he is telling the truth, Kay admits that Arthur brought him the sword. The three of them go back to the churchyard and put the sword back into the stone, and watch Arthur pull it out several more times. Once they realize that Arthur really is the King of England, they both get on their knees before him. This makes him very upset, and he wishes he had never seen the sword.