The offending article is now removed. How stupid do I feel. Just a square taper derivative in the end. Bearings still feel smooth but there is just a tiny bit of play. I guess it is on its way out.
So the issue we are now looking at is which of the following 3 options are going to be best:
A) Clean up the threads, apply a little grease and hope that stops the creaking till it goes in catastrophic fashion. With the caveat that it is on its way out.
B) Waste hours hunting down a replacement BB-ES71 113mm or fit a cheap one from CRC.
C) Tell him to put his short arms into his deep pockets and get an SLX and get with the 21st Century. (says the man with two bikes with Square taper BBs)
##EDIT### Found one on CRC for $30. plus $10 for postage. Seems like false economy as the rings look like they may well need replacement in the medium term.