I caught a swarm today. It was small - perhaps about the size of an orange once it had clustered. It was stuck to the side of the building where my out-apiary is. I suppose that it came from one of my hives.
I boxed the swarm this afternoon and then moved it to the roof this evening.
The swarm is surely too small to survive the winter so I'm considering adding it to hive H, which is has too few bees.
EDIT 12/08/2017 - this colony of bees had absconded from Hive H.