Years ago I was drying off in the changing rooms of the YMCA in Tottenham Court Road.

Over the loudspeaker, music was playing, the particular track was ‘Nineteen’ by Paul Hardcastle: “In World War Two the average age of a soldier was 26, in Vietnam it was 19: n-n-n-n-n-n nineteen…”

Next to me were two American guys changing, one said: “What is that about?”

The other one said: “I dunno just the usual anti-American bullshit.”

I wanted to interrupt and say: “I don’t think it’s anti-American, it’s anti-Vietnam, those are two different things. You can love America and still hate the war.”

But of course, being British, I didn’t say anything, just got changed and left.

But I was reminded of it recently by an article in the Spectator by a journalist called Douglas Murray.

The general thrust of his article was ‘Why the New York Times hates Britain’.

What he was actually talking about was that the New York Times hated Brexit, and they hated Boris Johnson.

I thought, this journalist is making the same mistake as those two Americans.

Many people think Boris Johnson is a twat, but they still love Britain.

Boris Johnson got elected for one simple reason: he wasn’t Jeremy Corbyn.

Most people would have voted for anyone except Jeremy Corbyn.

The main reason the media often gets it so spectacularly wrong is they automatically assume their view is everyone’s view.

They work, and drink with, a small number of people who happen to think like them, so their experience must represent everyone.

This detachment from reality reminds me of the election where the Tories equated patriotism with voting Conservative.

Their broadcast featured waving Union Jacks, Spitfires, and Land of Hope and Glory.

The message being you’re not a patriot unless you vote Conservative.

I particularly liked Dennis Healy’s response.

Healy was the deputy leader of the Labour party, he stood up in Parliament and said: “I look at the Conservative party’s benches and I don’t remember seeing any of those young faces on the beaches at Anzio when I was there in 1943.”

The blind belief that everyone thinks the same as us is a prelude to failure.

Years ago I was working with an agency that had been asked to look at Mars bars’ strategy.

Every strategist on the account was young, middle-class, and female.

Naturally, the first thing they said was it would have to be reformulated, it had far too much sugar, it would need to be healthier, children couldn’t eat it, it wouldn’t sell in its current form, it was out of tune with the zeitgeist of healthier eating.

But actually, young, middle-class women were never the market for Mars bars.

These people were trying to reformulate it into something that they would buy.

When I worked on Cadbury’s, the client told us that Cadbury’s made confectionary, like Flake, which was bought for taste, by younger women.

But Mars made what was called ‘gut-fill’, bought to satisfy hunger amongst men who did physical labour and boys who played sports.

Wouldn’t finding out who it was for be a better start-point than having the marketing team think: “Now what would I like?”

Isn’t it our job to be objective, not subjective?

As Mark Ritson said: “The first lesson for marketers is that you are not the market.”