On Wednesday 15th March 2017, Rugby Beekeepers Association held their monthly meeting and Speaker for the evening was Peter Spencer (Coventry Branch).
Peter's talk was "Swarm Control Plan B. (without finding the queen)" and was informative, enlightening and peppered with amusing beekeeping anecdotes that the members thoroughly enjoyed.
The process is described here (minus the anecdotes) for your consumption and depends upon one key piece of equipment that can be made from an existing crown board, or created from scratch.
A diagram of the modified board is shown here and you will see that one side of the board includes an entrance for the bees. As such, this side will need to be deeper than the clearance provided by the standard crown board. The clearance should be the same as that given by a standard hive floor, or an entrance block, approximately 20mm. The centre cut-out is a mesh of a similar gauge to that used in a varroa floor.

The images provided in this article can be clicked to see a larger version.
During your regular inspections, should you find preparations for swarming, (queen cells with larvae in them), these steps can be followed. It is important that there should be no sealed queen cells in the colony (Diag 1). If you find sealed queen cells, your bees have probably swarmed already and you are too late.
In an empty brood chamber, which we will call brood box B, place two or three frames containing pollen and eggs from your original brood chamber (A).
At this point you can select a frame of eggs from another colony, if the swarming colony has undesirable traits.
Shake all the bees off your selected frames and make sure there are no queen cells on these two / three frames.
Move the original brood chamber (A) to one side and place on the upturned roof.
Shake all the bees on the floorboard into brood chamber A.
Put the floorboard back in its original position and the new brood chamber (box B) containing the frames of pollen and eggs onto it.

You can make up this brood chamber with foundation or drawn comb. This is a good way to get new drawn combs.
(Diag 2) Place a queen excluder over brood chamber B, then the supers. On top of these supers place a second queen excluder.

(Diag 3) On top of this place the original brood chamber (A) with the queen cells and queen, crown board and roof. (Note from Editor : I suggest tearing down these QCs as my bees didn't do this job and they still swarmed)
(Diag 4) 24 hours later, go back to the colony, remove the top brood chamber and replace the top queen excluder with the modified floor, making sure you position the reduced entrance facing the opposite way to the main entrance.

Reassemble the hive and leave.
Background Narrative:
During the first 24 hours some of the nurse bees from the top brood chamber will go down to the frames of brood in the bottom box.
At the same time all the flying bees will be using the only entrance to the hive.
After the modified top floor board has been fitted, all the flying bees will leave the brood chamber containing the queen, thus leaving this part of the hive with only nurse bees.
Over the next few days the queen-right part of the hive will tear down the queen cells and the queen will be laying normally.
It is assumed that the bees in the bottom brood chamber start to make a queen cell containing a one day old larvae, then this cell will hatch around 11 days later.

(Diag 5) After 10 days the top and bottom brood chambers are swapped, i.e. the top brood chamber (A) is now placed at the bottom and the one containing the queen cells (B) is now on top. (The top entrance still needs to be opposite the main entrance)

At this point, you have an option:
- (Diag 6) You can remove all queen cells but one, if you are just going to replace the old queen.
Because the bees in the upper chamber have had contact with the bees in the bottom of the colony through the mesh they are still one colony and will not require the typical uniting methods (newspaper etc.)
- (Diag 7) Or you can select one or two queen cells and make up a second colony or one or two nucs.

N.B. The modified floor board can be used in a Bailey Comb Change with the mesh removed and as an eke when treating a hive for varroa in the autumn with apiguard.