I didn't really know what to expect from this. What I did not expect was for Steven Moffat to hit it not just out of the park but out of the city.
Firstly, the opening was superb. The hand mines were brilliantly realised and that reveal of the boy's name was something I did not see coming.
Having never watched The Thick of It, I had no idea just how funny Peter Capaldi could be. That scene with the guitar had me laughing out loud. However, this is not all a funny episode - Capaldi gets to show a wide range and has firmly nailed the Twelfth Doctor in a tale with links going back to the Fourth Doctor.
Clara Oswald is on fine sassy form in this episode; demonstrating the firm confidence of an experienced time traveller and also some very funny lines.
Missy returns here - no spoiler - and after the show doesn't even bother to explain how she survived last time (indeed makes a point of not doing so) manages to be even crazier than before. Michelle Gomez is adept at combining comic material with real menace; this version of the Master will kill just on a whim.
UNIT turn up again and there's some good material for them including a great gag about the mythical lost city of Atlantis for the fans - there are a lot of these in the episode.
The Daleks are also back - we get a smorgasbord of models going back to the very start. To say more would be spoilery, but I was impressed and I find the Daleks over used myself.
Lastly that cliffhanger is one of the best in the show's history. The solution may seem obvious but this is not a show that always goes for that. We shall see.
I don't tend to give top marks to professional works unless they are pretty much perfect.