THE WEB OF FEAR
Coming into this story with little knowledge of it, I didn't expect much. Indeed I had always considered The Abominable Snowmen to be the better of the two Yeti stories, though this was based purely on the surviving episodes of each story.
Put simply this is probably the best serial Troughton ever did. The action doesn't let up from the start, Lethbridge-Stewart has a great introductory piece and the Intelligence works better here than before in that it isn't treated as an in-your-face villain, this time running things in the background (or rather, out of sight of the audience for most of it).
My only point of contention would be the Yeti. Why were they brought back from a story perspective? They worked well in Tibet because they could be interpreted as the legendary beast but in 1970s London it just seems a bit silly. The robots could've resembled something else. The fact that the G.I also put all of it's energy into a single contraption that could easily be destroyed (the pyramid in Abominable, the mind draining machine here) is a little naff, but not enough to ruin the story.
It's funny that this story would mirror the following one (Fury from the Deep) with similar storylines, such as the fungus (seaweed) in a confined area of the london underground (north sea oil rigs) protected by people under the influence of the Great Intelligence (weed creature).
Celestial Toymaker next.