The royal brothers hit up London's Tonteria night club over the weekend for their longtime friend Thomas van Straubenzee's last hurrah as a single dude.
The future groom isn't a royal himself, but he's certainly no ordinary commoner (as if the van Straubenzee last name didn't give that away). Thomas is engaged to Lady Melissa Percy, daughter of the Duke of Northumberland.
The bride-to-be's family owns Alnwick Castle in Northumberland, which doubles as Hogwarts in the Harry Potter films (!). According to the Northumberland Gazette, the princes' BFF and Lady Melissa are holding their June 22 wedding at Hogwarts, aka the Percy family home.