- Harry: "Well, it'll be hard work, pretending to Aunt Marge I got to that St. Whatsits-"
- Uncle Vernon: "St. Brutus's Secure Centre for Incurably Criminal Boys!"
- Harry: "Exactly. It's a lot to remember. I'll have to make it sound convincing, won't I? What if I accidentally let something slip?"
- Uncle Vernon: "You'll get the stuffing knocked out of you, won't you?"
- — Harry Potter stands his ground against Uncle Vernon's threats.[src]
St. Brutus' Secure Centre for Incurably Criminal Boys is an institution for "mentally subnormal" and violent adolescent males. This was the centre that Vernon Dursley told his sister Marge he was sending Harry Potter to school. Saint Brutus is the patron saint for this school. Whether it actually exists, or was simply dreamt up by Uncle Vernon to hide Harry's true nature is unclear, although given that there is no Saint Brutus, it is probably imaginary.
In his third year Harry was forced to pretend he was being sent to St. Brutus's in exchange for Vernon's signature on his Hogsmeade permission form, because Vernon was so worried Marge would find out about Harry's true identity. As part of that ruse, he asserted that students there were customarily disciplined with a cane. However, as Harry unintentionally inflated Marge, he did not receive Uncle Vernon's signature.