We pull up next to each other at the lights - there are two lanes - and I hear a shout of "Are you f***ing stupid?"
I assume she's talking to her equally charming companion, but no, she means ME!
"Why are you driving in the middle of the road? You're on a little scooter - you should drive over to the side!"
I start to explain the principles of Advanced Driving, but before I can finish the lights are changing and she's shot off on amber.
I keep a respectful distance behind her over Waterloo Bridge, then inevitably filter past in the queue outside Waterloo Station.
As I go by, she throws her cigarette at me.
Normally I rise above road rage, but on this occasion I fear I raised a middle finger as I cruised past. I hope the cyclist behind me didn't think it was aimed at him.
Ah, sod it. I'm off to France in the morning - where they treat bikers properly.