The Edge of Destruction
This must be one of the few pre-Davison stories that I had neither seen on TV nor read in novelisation form. It's a two-parter, from immediately after the first Dalek story, featuring only the four members of the Tardis crew - the first Doctor, his grand-daughter Susan, and the teachers Ian and Barbara. There is a fifth character, not played by an actor, but I'll get to that.

This was very very brave. The production team had run out of money, and had to do an entire story with no guest actors and no sets beyond what had already been made. The two episodes had two different directors, one of whom had never directed a television drama before. It could have been a disaster.

In fact it is very good. I would even have said excellent, were it not for the bathos of the minor technical problem with the Tardis which turns out to be at the core of the plot. But apart from that - and one or two minor slips from Hartnell, though he keeps it together for the big set-piece speeches - I was surprised by just how good it is.

I also watched the DVD documentary, which is entertaining and enlightening, and also actually slightly longer than either of the episodes. Meta-text, isn't that the concept I'm looking for?