Thanks to all who responded regarding my problem re brood in brood chamber and
honey super.  Although some suggested that I may have had  a drone-laying worker
in the top box, all of the brood I saw was worker.  I revisited this hive on the
weekend just gone after having replaced the wire excluder with a plastic
slot-type last weekend. My suspicion was confirmed as I only saw very advanced
larvae and capped worker brood.  It appears that the queen was indeed getting up
through the wire excluder at will, and laying in the top box.  Surprisingly she
had to traverse a half-depth honey super to do so and had laid no eggs in that
box, instead preferring the upper older comb which already contained brood.

Thanks again for your responses.


Mark