Um, so, it's out. I just had the mother of all f#%k it moments and it has paid off.
I lifted the guitar up by the neck and I heard a very slight crackle, so I put one hand on the body, hung the neck off the edge of the table and pushed down. Not that hard. Off it came. For some reason there was copper tape under the end of the neck tenon! WTF?
Sketchy. I'm so surprised. I was not expecting that to happen at all.