Timely... I had one today.
I showed up on time, ate, made sure my boss saw me there, grabbed a cup of coffee on the way out, quietly left, and got back to work.
The room that it was held in was way too loud, and the two women who continually kept trying to laugh louder than the other one (like it was some sort of competition), helped me to decide when it was time to depart.
As far as the two women, these two are annoying like that. Unfortunately, it could be easily expected out of both of them. There's never any doubt when they're in a room. And there weren't any Rum balls either.