Well the hive in my back yard has got some capped Queen Cells in it! But the existing Queen is still there. So I removed the Queen Cells and put them in my mating box! I'm not sure if the hive will swarm - probably it will - unless I can perform an "artificial swarm" on it. However, given the weather forecast I think this is unlikely before Sunday. And by then it might be too late!
Still, I hope I'll have another Queen to raise which I can use to split another hive! I'll check in the mating box in a week or so to see what's happened!