That's it, there, on the horizon.
Zooming in, it was possible to see some of the action. This is a mouse about to meet a dodo:
The view through my telescope was much better, as I could see the individual drones close-up. I needed a more stable base for it than one leg on a windowsill, though.
Most of the images were static, with movement coming from turning lights on and off (Cheshire cat fades leaving only its grin, smoke appears from a chimney — that sort of thing). I thought they'd maybe have used animation software to produce the necessary controls, but it was more a 3D-printing set-up by the look of things. Still, I might go to one if there's a better subject, as it does look the kind of thing that's worth seeing at least once.
The most important take-away is that I now know for sure where Castle Park is when viewed from our house.