Radio City Music Hall - NY 7/7/10
Apparently Joe Walsh (Ringo's brother in law) and Barbara Bach were responsible for getting Paul there and keeping it a secret.
Walsh, Derringer, Bissonette and Paul had an early afternoon rehearsal to practice the song, long before Ringo or anyone else arrived.
Paul snuck into Radio City right when the show was starting and watched it from the last row before heading backstage at the end.
Ringo was completely surprised, not expecting to see Paul at the show.
http://www.youtube.com/watch?v=p5sgVi88SXU