This is an odd story, even by Doctor Who's standards! I really like the concept of an alien planning to steal Earth's minerals in an attempt to break the speed of light, and the stuff with Persuasion and Enlightenment taking on the form of Tegan's drawing is a really clever one.

I also think it's worth noting that even though Peter Davison admitted to feeling nervous during the recording of this serial (it was the first story he filmed), it really doesn't show. He seems so comfortable and confident in the role from the start, a bit like Matt Smith did in the first story he shot, The Time of Angels/Flesh And Stone.

Tegan is really annoying in this story though. I really hated her when she just straight up abandoned the Doctor and the others and left in the TARDIS at the end of Episode Three. I mean, what the hell, Tegan? Shows how much you care about them.

Also: Monarchy is way too easily defeated at the end. All the Doctor does is chuck the poison at him and he's shrunk. I was expecting a little more.

Overall a pretty good story.