Severus had been watching the attendees arriving and had arched an eyebrow on more than one occasion. Draco was indeed going all out with this. He had drawn people from right across the social spectrum, some of whom Severus was surprised to see here.
Percy Weasley was one of those. The most tolerable of the Weasleys after Bill, he was however a stickler for rules and regulations. It was unsual to see him at something so clandestine. Still Umbridge could hardly be easy to work with and she would dislike the Aurors' independence intensely. If she hadn't already, it would only be a matter of time before she made a powerplay there so perhaps Weasley was interested in stemming that before it started. If so, it spoke well of the young man.
Oliver Wood was less of a surprise to see here though given what Titchy had told him and the lack of progress reports he had been receiving it was entirely possible that Oliver should have been in his workroom rather than at Escapism.
Severus worked his way around the room, sticking to the shadows until he was able to glide silently up behind his apprentice. "While I am aware it is the summer holidays, I am afraid that only applies to the students at Hogwarts, not apprentices."