A good hour and a half of focused writing in a quiet environment, followed by optional drinks at the bar. It's a very productive and cheap way to write without the usual distractions. There's also no obligation to share or criticise, and you are welcome to work on whatever you like - stories, blogs, academic work. It's simply a quiet space for writing.
The session is hosted in the 'Green Room' - upstairs on the left. (Sometimes the upstairs is cordoned off by a rope, but you can ignore this, and just go on up).