But Uncle Vernon wasn't going to give in without a fight.

“Haven't I told you he's not going?” he hissed. “He's going to Stonewall High and he'll be grateful for it. I've read those letters and he needs all sorts of rubbish — spell books and wands and—”

“If he wants ter go, a great Muggle like you won't stop him,” growled Hagrid. “Stop Lily an’ James Potter's son goin’ ter Hogwarts! Yer mad. His name's been down ever since he was born. He's off ter the finest school of witchcraft and wizardry in the world. Seven years there and he won't know himself. He'll be with youngsters of his own sort, fer a change, an’ he'll be under the greatest headmaster Hogwarts ever had Albus Dumbled—”

“I AM NOT PAYING FOR SOME CRACKPOT OLD FOOL TO TEACH HIM MAGIC TRICKS!” yelled Uncle Vernon.

But he had finally gone too far. Hagrid seized his umbrella and whirled it over his head, “NEVER — ” he thundered, ” — INSULT — ALBUS — DUMBLEDORE — IN — FRONT — OF — ME!”

He brought the umbrella swishing down through the air to point at Dudley — there was a flash of violet light, a sound like a firecracker, a sharp squeal, and the next second, Dudley was dancing on the spot with his hands clasped over his fat bottom, howling in pain. When he turned his back on them, Harry saw a curly pig's tail poking through a hole in his trousers.

Uncle Vernon roared. Pulling Aunt Petunia and Dudley into the other room, he cast one last terrified look at Hagrid and slammed the door behind them.