I listened to this yesterday and while I liked it, honestly, without getting to guide up to remember the title I would've completely forgotten what happened.

I remembered the reveals and that, but the actual events, less so.

The reveal of what's going on with Robin's Dad and Mr Bird was a fun one, the Mr Bird twist especially was something I managed to figure out just before it was explained in story which I think is a mark of good story telling. The title as well being about the trains and timelines is also a fun little detail

Colin as The Curator here is lovely and the highlight of the story for me, though of course it's going to be, it's Colin. The stuff with Tanya, mirroring what we saw in UNIT Dating, is also done really well, and the explanation that the 2020 we're following is a parallel/alternate/possible 2020 is an interesting one and helps make sense of some of the wackiness we've had with time travel in the series before now.

It feels like it's more setup than anything else though, which on the one hand is good to have, but on the other, well, makes for a forgettable story.