A friend tells me that when I started by first job in an investment bank I did not speak for the first three weeks. He exaggerates, but not much. What I was doing was working out the unwritten rules of how to behave in an alien environment.

I was reminded of this by reading Tony Connelly's description* of Geoffrey Cox's behaviour last week in Brussels: he boasted of not having visited the city for 40 years and angered Sabine Weyand by calling her "my dear." Mr Cox did not do what I did - shut up until you've learned what to do.

Herein, I think, lies a class difference. If you are upwardly mobile from a poor background, you have to learn how to fit in. If you are posh, you don't. You glide from school to Oxbridge to the city or bar all the time surrounded by like-minded people so you know the rules. The upshot is that in the unusual contingency of ever being outside of that environment - as Cox was in Brussels - you put your foot in it.

We should read Cox's behaviour alongside Boris Johnson's claim that the inquiry into historic sex abuse is money "spaffed up a wall". (Mr J, of course, is no stranger to wasting public money). Both, I suggest, are examples of the arrogant insensitivity that results from not having to work out how to consider the sensitivities of those outside your group. (When those sensitivities are upset, of course, it is political correctness gone mad, rather than what it is - the result of crass behaviour.)

At about the same time I was in purdah my contemporary Mr Johnson was being sacked by the Times for lying. Which highlights another class difference. Those of us from poor backgrounds know we don't get many chances so we must take those we get: there are no second acts in working class lives. Had I been sacked from my first job for dishonesty, I doubt I'd have got another chance. Posh people do get other chances. And both sides know this.

My point here should be a trivial one. Background determines character, so rich backgrounds tend to generate different characters than poor ones. I'd suggest other differences, all of which should disqualify most posh people from politics:

1. If everything comes naturally to you, you don't need to think so much about how to get it. So you under-invest in learning how to hustle, negotiate or strategize. (Is it really an accident that the western politician who most mastered these arts, Lyndon Johnson, came from a poor home?) This might be one reason why Brexit has gone badly. Having spent his entire life thinking he could get what he wants simply by asking, Jacob Rees-Mogg has been disturbed to find that the EU doesn't work like that.

2. Posh people have confidence - too much of it: it was overconfidence that led Cameron to call that referendum. Because people mistake confidence for actual ability, this lends them a credibility denied to others, which is reinforced by the dominance in the media of other posh folk. If Johnson and Rees-Mogg had thick Brummie accents, how would the media treat them?

3. The rich don't appreciate just how important money is. For a poor family, an extra fiver at the end of the week can make the difference between relief and misery. This warps their political priorities. Whereas I regard economic growth and redistribution as the main political issues, the rich have others - Brexit if you are on the right, Palestine if on the left.

4. If you are surrounded from birth by other rich people, you lack a gut understanding of how others live. You are prone to the middle England error - of over-estimating the incomes of ordinary people. This means that even the most well-meaning are apt to conflate the national interest with that of the wealthy. What's more, you never get a true grasp of what poverty really means. It's not just about a lack of money, but about a lack of opportunities and role models: the first people I met with degrees who did not work in the public sector were the guys who interviewed me for that investment bank job. And it's about insecurity too: if you are "just about managing" you are only one decision away from abject poverty. One of the greatest days of my life was the realization, sometime in my thirties, that I would never be homeless. Some of you reading this won't understand that. As one of the key texts on class has it:

You will never understand
How it feels to live your life
With no meaning or control
And with nowhere left to go

5. Trust. We naturally trust those like ourselves. Which means that posher politicians are apt to surround themselves with other posh people. This isn't a purely rightist trait: think of Andrew Murray and Seamus Milne working for Jeremy Corbyn. It also means they are more likely to take advice from other posh folk, leaving then vulnerable to undue influence from the rich.

Now, I should caveat all this. It is possible - with effort - for the rich to understand this. One or two do. But even for these, there's something missing. Just as religious converts lack the visceral knowledge of their faith that comes from having been raised in it, so posh people lack such understanding of poverty. As Bill Shankly said: "the trouble with you son is that your brains are all in your head." Perhaps the tragedy of Tony Blair embodies this. His success lay in an awareness of what mattered to working people: money and crime. His failure came when he forgot this and was seduced by foreign policy.

Here, though is the thing. Despite Disraeli's famous quip that rich and poor are two nations formed by a different breeding, This hasn't always been the case. For much of the 20th century there was a massive mitigation of these tendencies. Military service forced posh men into close relationships with poor ones, thus broadening their perspective. As the Times' obituary of Lord Carrington says:

He found himself sleeping in a hole beneath his tank with his four crew who came from poor backgrounds and had suffered hardship during the pre-war years. The experience shaped his politics, he said later. "You could not have got a finer or better lot than they were. They deserved something better in the aftermath of the war.

This is not atypical: in my first job most equity salesmen had army backgrounds and so were accustomed to working with people from working class backgrounds.

One cost of living in a less militaristic society, however, is that this influence is much diminished and that posh men are therefore more distant in consciousness from the rest of us: the contrast between Lord Carrington and Boris Johnson - both former foreign secretaries - perhaps embodies this.

* an account which shows that Irish coverage of Brexit is an order of magnitude superior to the British.