Maybe there was a Great Grey Shrike about?!
I can't believe that is self inflicted, surely it's Shrike?
I thought of that, but I really wouldn't regard the site as suitable for shrike.
To be so impaled it would have had to have been flying at a fair speed ....
... and at a funny angle, but if it was a shrike, then it must have only been there briefly, as it is quite and enclosed spot, but I suppose, it might be possible. I collected the moth, so I'll have a look at it, to see if I can see any other damage to it. There were no other impaled creatures around the place that I could see.