Yep, they're definitely doing invitation-only events on the "dark" nights. Someone from a PR firm posted a photo of the special invitation. She's since deleted the tweet, but it's captured here: http://insanely-smart.tumblr.com/post/165294258543/twittercomprmattersukstatus907907769193209857

I saw a few other tweets about last night's event - another PR person, an agent, and one random guy.