The complicated rearrangement of Hive C left a problem: a gap of a few millimetres where the nucleus box meets the hive body. Every time I approached the hive the bees from inside behaved defensively and I smelled the distinctive alarm pheromone (it's an ester somewhat like Bananas).
I had tried to block the hole using a hive tool pushed up into the gap. The hive tool fell out. I shoved folded newspaper into the gap but the bees became so angry I decided to back off before all the gaps were filled. I thought that the gaps were filled but I was mistaken. The bees were quite cross.
This morning I returned with tape. The gaps are all now taped up. I hope that the bees calm down now.