Mud wasp. Or “mud dauber” as the late Mr Daniels would say.
I just finished watching the last episode of the “Endeavour” series, and I really hope they make a seventh season, because this one was about tying up loose ends and a bunch of new starts. I will now start to watch them from the first season again. Excellent actors. Stupendous writers! Worth watching, for sure.
Paper-wasp, not a mud-dauber. We get both kinds building nests all over at Cub Scout camp.