My hives are surrounded by at least half a dozen wasps which want to rob them. They zig-zag in front of the entrance; they crawl in under the Varroa screen; they wait at the edges and drink from the water tray. They want the honey but they can't get in.
All of the hives in central Oxford have small doors and strong guards. Three of the four have at least 20 bees visible on the outside of the hive entrance. One hive had fewer visible but appeared to be just as effective at guarding.