It's just a bit boring. I've seen it at least twice but nothing ever made much of an impression apart from Alpha Centauri—and that wasn't the right sort of impression.

The clearest thing I can say is that I preferred The Monster of Peladon. Not sure I could say why, and I might feasibly change my mind in the future. But I found that story more engaging.

I don't like the idea of Jo and Mike Yates as an item. That is really the only flaw I can think of. One of Pertwee's very best in my opinion.