A collection of emergence holes around the base of a hybrid poplar tree. The hole on the right appears to contain the remains of a cocoon.
No interactions present.
I agree it's one of the sesiids, but I don't know how it would be separated from S. bembeciformis by its holes (as it is also found in poplars, though usually in Salix),
I'm not sure about the link between bembeciformis and Poplars.
Similarly apiformis is solely associated with Populus, although not just P nigra.
Of course, the proof of the pudding is in the hatching, but getting a view of a Hornet Moth involves a good bit of luck.
Lat/Lng: 52.0, -2.4
OS grid ref: SO7636