I stopped to help a chap with an upside down Foffa. He was turning his spanner on the non-drive side nut (which I noticed was quite rounded, being made of poor quality material), and it was just spinning. I advised him to stop, as the threads were probably stripped, and it wasn't going to get any better.
I didn't have anything which could help him. First time that's happened.
Even a load of washers to step the nut out onto a better bit of axle thread (assuming there was anything left inside the nut to grip with) would have worked, but I didn't have anything.
He showed me that the wheel wobbled on the axle, too, which he thought was part of the same thing, but was just loose cones. Bit of a rubbish wheel, really.
We were between Stockwell & Oval, and he was on his way to Blackfriars. My best suggestion was Brixton Cycles, but it was somewhat out of his way
I just had to apologise, remount and carry on. I feel sorry for the poor chap, and rather embarrassed myself that I was no use.