Harry Potter and Defense in Depth

This montage from "Harry Potter and the Sorcerer's Stone" filmically illustrates the security principle of defense in depth, as explained by Bruce Schneier in his book "Beyond Fear":
"In J.K. Rowling's first Harry Potter novel, Professor Dumbledore arranges to protect the Philosopher's Stone (the Sorcerer's Stone, in the American edition) not with one but with a series of countermeasures: Fluffy the three-headed dog, devil's snare plants, a locked door with flying keys, a giant chess puzzle, a troll, a logic problem involving potions, and finally a magic mirror. An attacker would have to penetrate every one of them, rather than just the weakest of them. Security is not just a matter of numerous countermeasures, but countermeasures that work independently and in series and that present different sets of challenges to the attacker. In general, a moat-wall combination is better than two walls" (p. 105).