People love Dr Who for different reasons. I've never heard anyone say (about the old series) that they love it for it's believable monsters and amazing special effects. Yes, they're cheezy. But actually not bad for their era.

Having seen many of the earlier episodes, this is an above average story for it's time. It seems Patrick Troughton very much embraced and his role as the Doctor, even appearing in three seperate multi-Doctor stories after his tenure was over. I think that this is a story made even better by his performance in particular.

Also, you can't help feeling the story was inspired by current events, being based on how humans were flourishing on the moon; at a time in real life when mans first step on the moon was mere months away.

One of the best serials from the Patrick Troughton era.

I'll admit it: I was a kid when this was repeated for the Silver Jubilee celebrations in 1988, and I watched parts of it through the crack in the door from the kitchen. (My little brother could never be frightened by anything not in colour, but not so me.) This is one of the few stories that still grips and frightens me as an adult, if in new ways. Fewsham's dilemma is real to me in a way it never was for my younger self. The vulnerability of the Earth and the way that new and near-ubiquitous technology can make us more vulnerable to attack or disaster and not less hit home in a way they never could for a child. This isn't just bug-eyed monster stuff, this is actual sci-fi.

There's innovative camera work here which is very effective. The Doctor is written out for an episode (actor's holiday) in a way that works so well you mightn't notice. The guest cast are mostly spot-on. Women are allowed to get things done instead of merely being rescued all the time. The bad guys have a plan that makes sense, and motivations you can believe in. And the story presents a threat to Earth you can genuinely believe ordinary people would give their lives to stop.

This looks beautiful on DVD, and the special features are moderately interesting. As always with a story of this length (it's a 6-parter) you'll notice some padding, but on the whole the pacing's excellent and this is a real gem of the Second Doctor Era. I'd consider it the essential Second Doctor DVD purchase, actually, ahead of Tomb of the Cybermen. Highly recommended, and accessible to new viewers.

This story has been re-released more recently in one of the Revisitations box sets, with extra special features, so consider buying that set instead if you're interested in the other stories it contains.