Accidental success.
I mentioned in another thread that I had acted prematurely in replacing what I thought was a missing queen, the outcome was positive, here's what happened:
I made a plait after the old queen swarmed from my main hive, putting one QC into a nuc and leaving one in place. Both hatched, but believing the new queen from the main hive to be dead, I decided on a fairly risky reintroduction of my surviving queen by lifting her and two frames of brood and workers from the nuc and just inserting them into the hive, hoping for the best.
So I removed two frames from brood box and replaced these with two from the nuc, leaving the frames just outside so that the workers could transfer the stores. As evening approached I went to shake off these two frames only to discovered the not so dead queen #2. With nowhere else to put them I dropped the two frames into the nuc to let the bees sort it out for themselves.
In short: I'd taken two frames from each hive and swapped them over complete with attending workers and their queens.
So a week on and I have two healthy queens and a lot of capped brood. No sign of any bee casualties.
An important factor in this may be that the queens are sisters and so genetically identical, and all of the workers are sisters to both the queens also.
So no drama but a fortunate and interesting result (at least I think so).