Now then, there is no doubt that this is one of the best Doctor Who stories of all time but... (whisper it) ... part four isn't really the story's finest 24 minutes. It's a lot of wandering around on a set. Your host Toby Hadoke approaches it with trepidation, not having had a lot of the padding of this episode as part of his childhood viewing on VHS (it was cut from the BBC release). So will this end on a damp squib, or can guest Richard Bignell's enthusiasm get everyone to the finish line?