It's from the South Bank Show, that was shown a couple of days ago in Britain. They followed Ian McKellan around for a year between June 2003 and June 2004. You got to see the Wellington premiere, and Ian's last day of shooting, Viggo and Orlando mugging it up for the camera-crew and Liv acting like a Polynesian princess!
Worth seeing if you can dig it up! I'm sure it must be on the net somewhere!