Thanks - interesting.
I rode 100km on it on the night. I knew something was wrong with the wheel from the braking but thought it was a spoke, but I checked them and they all felt ok. When I saw it in the daylight the next day, I decided I didn't want to ride on it again and swapped the wheel out. I was concerned about the rim becoming fragile as well as impared braking. It looks like that was the right decision: I'll get a new rim.