Shada (if I can jump in) was a Douglas Adams script for Tom Baker's Doctor, which never got filmed due to a BBC strike. Adams turned some of the story into _Dirk Gently_ -- this is the echo: the elderly professor whose apartments at Cambridge (or the art gallery) happen to be a drydocked TARDIS.

I had *so much fun* watching the anniversary show.

(And I watched it with a friend who had never seen any of the new series. It was terrific for her too. Moffatt is inconsistent, he's blown stories before and will surely blow them again; but this one, out of the park, over the county line, still going.)