The Secret Orchard, as fred quimby said. You will probably be able to get in, maybe right up by the fence, I mean the perimeter fence. I have seen shall we say spacious bell tents go up that late, but really squeazed in awkwardly close to neighbours. You might stand a chance.
As for the Pass Out question, security stuff does change one year to the next, but I usually go out and back at least once, never been heavily searched on returning. I am not promising anything, and others may have different experiences.
