I was crossing the road in St James’s Square when an approaching car slowed, and a man gestured from the open window. His respectable suit jacket was on a hanger inside. I knew exactly what was up. It was a con trick.

How I knew so immediately is not easy to tell, except that I’d experienced something like this before. That time it had been in the street next to the Royal Hospital in Chelsea, where the red-coated Pensioners live.

The man on that occasion had told me some story about having to catch a flight to Italy and having lost his credit card. I could soon see that it was concocted.

The trouble with confidence tricks is that they annoy us, the victims, by showing us up as fools. In a pious mood, I am quite prepared to admit that I am a fool.

But a little thought (which is seldom served up on a plate with a sprig of parsley) demonstrates that to carry on daily life we must regularly all be as trusting as any mug in a con trick.

We hand over a £20 for a cup of coffee, confident that generally we won’t be handed change for a tenner. We flip a letter into a pillar box, never fearing that this smart red shrine to civil order will be put to the torch.