I'm honestly a bit torn on what to think of this one. First, on the good side: the premise is excellent, the aliens are decent, Strax got some good jokes in and Vastra got to use the fact that she wasn't human.

On the other side, however, the threat was basically an enemy ex machina, with only the barest hints to the enemy before the last 10 minutes. Additionally, this story isn't anchored to the series. There is nothing tying the story to Victorian London, or even the Paternoster Gang specifically, and neither does the atmosphere really distinguish it much from a standard Who story. I may just be a bit harsh on this series but I'd have liked some more involvement of the era. Perhaps they could have involved the groups living in Victorian London more or made it a point that maybe Victorian London does not cater to the tastes of the ambassador well, leading to problems. They could have left out the enemy they currently have in my opinion in favour for more series-specific problems.

So while it was entertaining, I'm still waiting for something that only this series can do.