It was such a hot day and neither of us really wanted to spend hours in our bee-suits but we didn't really have a choice.
We spent about three hours going through the hives one by one, removing drone larvae, adding new boxes and generally checking that everything is OK. We took the smoker with us, and the bees were very calm. We managed to get a lot done.
One of the hives seems to have a bad varroa infestation but apart from removing the drone larvae, there is not much we can do about it now.
We've been thinking about the queens and will probably get new ones for some of the hives in late summer.