“My mother,” said Ron on night, as they sat in the tent on a riverbank in Wales, “can make good food appear out of thin air.”

He prodded moodily at the lumps of charred gray fish on his plate. Harry glanced automatically at Ron’s neck and saw, as he has expected, the golden chain of the Horcrux glinting there. He managed to fight down the impulse to swear at Ron, whose attitude would, he knew, improve slightly when the time came to take off the locket.

“Your mother can’t produce food out of thin air,” said Hermione, “no one can. Food is the first of the five Principal Exceptions to Gamp’s Law of Elemental Transfigura—”

“Oh, speak English, can’t you?” Ron said, prising a fish out from between his teeth.

“It’s impossible to make good food out of nothing! You can Summon it if you know where it is, you can transform it, you can increase the quantity if you’ve already got some—”