I'm impressed with how long the story commits to the idea that the Tenth Doctor has regenerated into a Gemma Whelan incarnation. Obviously, this isn't the case, as we got Matt Smith after David Tennant on TV, but the story makes you wonder for a while whether this is somehow a legitimate incarnation.

The reveal is teased well throughout, with the Tenth Doctor breaking through to Anya Kingdom from the future. When the twist comes that Gemma Whelan is actually the Monk, it feels extremely satisfying, because of the hints in the first two parts of Dalek Universe which suddenly make sense when her identity is confirmed. Gemma Whelan makes for an excellent Monk, and bounces off David Tennant extremely well.

The latter half of the story, with time collapsing on itself, reminded me a lot of The Wedding Of River Song. It has the same concept of elements from past time periods emerging into a future time, with prehistoric animals and cavemen roaming the streets. In my view, it handles it better than The Wedding Of River Song, as it feels much more coherent, and less of an unruly mess.