I'd seen him coming of course, and heard that Germanic swooshing engine and roar of air conditioning, but I assumed he was going straight on.
'Why didn't you indicate, you fat git,' I yelled, leaping for survival in a tangle of lurcher and M&S cartons. I might as well have been yelling at a passing jumbo jet for all he could hear through the sound-proofing.
If he had heard, he'd probably have been baffled. Because clearly nobody does indicate any more.
The man in the Mercedes isn't just an isolated selfish bastard, I have come to realise. Sometimes it's a Ford, or an Audi - occasionally the driver is a woman, or sometimes not even fat. But in London it's become normal not to signal. I almost feel like tapping on the window when I see somebody stopped at a junction, to ask the driver which way he plans to go. Or has he not made his mind up, and would he like to point or wave, or something when he has?
It's as though driving has become, for most people, one of those motor race computer games. Like cars, computers have a speaker to make a noise, a button to go faster with, and a button to steer, but there is no indicator stalk.
It's not just pedestrians they ignore. I can be on my bike at traffic lights, next to the curb waiting for the lights to change so I can cross Tottenham Court Road. There's a series of junctions like this when you cross London east-west, Marylebone High Street, Baker Street, and so on. The lights change, I set off, and the driver doesn't go straight on, he swings left, across in front of me.
Partly, I suppose, bikes and pedestrians and dogs are small and quiet, and so not worth the effort of moving that finger a quarter of an inch to signal. But these drivers don't even give clues to other cars.
I began to think maybe the Government had changed the rules, so I checked the latest Highway Code. There they still were, those dinky little cars in diagrams with little flashes on their corners. 'Mirror, signal, manoeuvre,' it says. Couldn't be clearer.
Maybe out of London it doesn't matter so much, with virtually every shopping street pedestrianised, every town a one-way system linked to the next by a dual carriageway.
But London still has all these clever back doubles, and it really would help it to keep moving if people would give clues. Maybe these new privatised traffic wardens are the answer. Never mind illegal parking, if they spot a non-indicating car they should jog up to it in the next traffic jam and slap a fixed-penalty notice on the windscreen.