I was inspecting a recently joined hive, and noticed some new queen cells, which I tore out -- and then I saw the Queen, who was piping a bit... I watched her run around the frame for a while, thinking she was a little small, yet definitely longer than a virgin.
After clearing all queen cells from the top box, I moved it (along with her) off onto the upturned lid on the grass, and then this began to happen:
I like how these girls are just chilling on the grass waiting for the swarm to make up its mind:
And I'm not sure if it's because the box was separated from the rest of the hive, or because I had torn out the queen cells, or both, but the swarm aborted and landed back in its original box:
Afterwards I moved this box aside and made a new hive -- easy split!