The minute I lifted the feeder off the crown board, bees started coming up the feed hole like they meant business. Covered hole with a tile. Cracked the crown board to the accompaniment of angry buzzing, moved it along so most of the frames were still covered so I could hopefully just pull the end one. Annoyed bees trying to get out of the small gap I had left, reached for my smoker to find it had gone out
Decided I wouldn't bother trying to pull any frames given the mood the girls were in so slid the cover board back, quickly tried to get the tile off and feeder back over the hole before too many more could get out. Put the feeder eke back on but quite a few bees on the cover board refusing to move and loads all over the front of the hive.
I put the roof back and stayed around for 20 minutes in the hope they would calm down enough for me to take the roof back off and brush off the bees trapped in the eke, I watched a few wasps and opportunists being repelled by both hives and lots of bees coming in with (presumably) ivy pollen and nectar. They were still quite agitated though, pinging off my veil and buzzing angrily in my ear, so in the end I decided it wouldn't be successful and they would have to stay where they were.