Appreciate all the info.
I had a very quick chat with him so I'm short on detail.
He originally had an oil burning issue and traced it to the bore. He had it bored out to +80. He eventually got the barrels relined back to standard by Norvil but after 90 miles the smoking started.
He was checking the bore & is convinced it's oval, he says he can see marks from the piston rings only on some parts of the bore but not on others.
He was waiting for a loan of a cylinder bore gauge so he could verify his theory.
This chap has rebuilt a lot of brit engines, Triumph, BSA & Norton so he knows his stuff, this particular problem has him stumped.
His plan is to get another set of barrels, put the engine back together & see what happens!!