"The Last Day" is the latest short mini-episode leading into tomorrow's Doctor Who 50th anniversary special, "The Day of the Doctor". The prequel was originally released exclusively to iTunes a couple of days ago, but is now available on the BBC's YouTube channel.
The story details the "fall of Arcadia", which has been mentioned by the Doctor before (although I'll confess I can't remember which episode at the moment; it was a tenth Doctor episode). Really, it doesn't tell a whole lot, and is far less entertaining than "The Night of the Doctor". However, it does set up a nice sense of ominous foreboding for the special.
Just one more day to go (three for me)!