So, doesn't just maintain the high level, but reaches even higher. Thoroughly entertaining throughout. Music, FX, direction all stellar. Karvanista even more enjoyable, villains even more menacing and intriguing, Dan starting to engage, and yes, as practically everyone else has said, so good to see Whittaker's Doctor finally being proactive, finally driving events.
The single-mindedness of the Sontarans, to the point they never once looked behind them, was amusing, and I always enjoy a little satirisation of military attitudes and habits. The same issues apply as with the first episode, but they're easier to overlook in this one, and it does actually feel like all this is going somewhere. I also found the audio mix problematic at times, effects and music overpowering dialogue, but that's far from unique to Who; a little acknowledgement that many people don't have the latest cutting edge surround sound tech would not go amiss in film and TV.
One last random thing, and it's possible I didn't register it or it's slipped my mind, but what happened to the gent from the 1820s? He appeared on Planet Time, Yaz spoke to him, then he just...vanished. Wasn't seen again. Plot just needed us to know he was there, then he got put into storage until his services are required again, maybe. Have to admit I love the inclusion of these real-life inexplicable tunnels - which I hadn't heard of before - and really hope they serve a satisfying purpose.
This is genuinely good, fun, interesting stuff, and I'm crossing everything that Chibnall can stick the landing, for his sake as much as anything else. Four more episodes to find out...