My favourite from series 1. The main highlight is the sensorites themselves. I just kind of love how slightly pathetic they are compared to most aliens given a full costume. Its just fun for me to watch them bicker in soft-spoken voices and give a bunch of information about their world. Their designs and alien city sets are also just a lot of fun. It's definitely more of a dialogue heavy episode, but I'm fine with that. The twist villain should probably have been revealed earlier also, but I don't find it too bad as it currently is since I just enjoy watching the sensorites.