That moment Uncle Vernon snatched the letter from Harry's hand and it said Mr. H. Potter The Cupboard under the Stairs 4 Privet Drive Little Whinging Surrey Shaking the letter open with one hand and glancing at it. His face went from red to green faster than a set of traffic lights. And it didn’t stop there. Within seconds it was the greyish white of old porridge. (Rowling, J.K. Harry Potter and the Philosopher's Stone (p. 37). Pottermore Publishing. Kindle Edition.)
Vernon! Oh my goodness – Vernon!
Dudley tried to grab the letter to read it, but Uncle Vernon held it high out of his reach. Aunt Petunia took it curiously and read the first line. For a moment it looked as though she might faint. She clutched her throat and made a choking noise.
They stared at each other, seeming to have forgotten that Harry and Dudley were still in the room. Dudley wasn’t used to being ignored. He gave his father a sharp tap on the head with his Smeltings stick.