Christmas is the season of goodwill, even towards our relatives, whose behaviour we find so hard to forgive at other times of the year. But do others really behave better than our loved ones? Christmas is a good time to reflect upon the manners of our fellow man; and in Britain, our reflections are unlikely to be reassuring. Our manners are coarse, and getting coarser.

For example, I can usually tell that a young female patient attends university. Almost without exception, she tucks her feet under her and puts them on the chair (almost with the air of one performing her duty) when she sits down in my office. She is genuinely surprised to learn that other people must later sit on the same chair, and would probably prefer that she did not put her feet on it.

This is but a small example of the gracelessness of modern British manners. Other such small examples I have noticed during consultations are the non-removal of baseball caps, the continued eating of snacks and the failure to switch off mobile telephones (a doctor friend of mine told me how one of his patients actually continued a conversation on her mobile phone while he was conducting a gynaecological examination on her). The British give the impression of being modern barbarians.

This barbarism is classless, but it strikes me as none the better for that. It is no consolation at all that the rich and well educated behave as badly as the poor and ill-educated, that vulgarity should be universal. Nor is it true that boorishness has always characterised the British. For example, I am often struck by the good manners of elderly working-class people, who are not necessarily well educated in the formal sense, but who nevertheless know how to behave well towards others.

I recall an elderly working-class widow who has experienced many tragedies, none of her own making, who recently lost three of her four children unexpectedly. She told me how, in the privacy of her own home, she often cried, but how she did not do so in public because "it wouldn't be right, would it, doctor?"

Others, she said, had to get on with their lives without being inconvenienced or embarrassed by her, and so she kept her grief to herself, without making a public exhibition of it.

This fortitude struck me as noble, though it was much against the temper of the times, which is all in favour of emotional incontinence. That even in the depths of her grief - which I knew to be great - she was able to think of the convenience of others demonstrated how ingrained was her devotion to mannerliness. And I could give many other such examples.

I do not think the better manners of older people in Britain are just a reflection of their greater chronological age. It may be true that people grow less aggressive as they mature, but there are many ways to be uncouth besides outright aggression.

It is the delicacy of feeling and the awareness that, in social interactions, other people count as much as oneself that seem to have disappeared, and modern Britons will not necessarily recapture them with age. The extreme individualism of our time - a poisonous concoction of rampant consumerism and belief in the endowment of the individual with endless, but largely denied, rights - is not conducive to good manners or consideration for others in the small interactions of daily life. No nation of perpetually disgruntled shoppers will ever be notable for the grace of its daily conduct.

Are good manners really important? Certainly they make everyday life more pleasant, but it is perfectly possible for a man with the best manners to be a complete scoundrel, just as it is possible for a man with the roughest manners to have a heart of gold.

The question is akin to that of the morally educative purpose of literature: if it really has one, why is it that well-read people do not behave conspicuously better than those who have never read a book in their lives?

There was a conflict between my parents as I grew up as to the importance of manners. My father believed that a good heart was more important than adherence to what he considered an arbitrary code of conduct: indeed, he believed that such a code was likely to stifle the expression of man's natural goodness and thus lead ultimately to worse conduct.

My mother, by contrast, was a firm believer in outward convention. I had always to tip my school cap to the driver of a car who stopped to let me cross the road. I learnt very early that a man should walk on the outside of a woman on the pavement, and to this day I suffer agonies of internal discomfort if, for some reason, I am prevented from doing so (and many women nowadays do not even understand why I want to change sides as we cross the road).

To a certain extent, manners in my childhood were taught like military drill, though I am painfully aware that, despite this, my manners are less good than those of people born a generation before me. Far from seeming to come naturally, as the best manners do, I quite often have to remind myself consciously of the canons of good conduct. And, like an old sinner, I often lapse.

When I was young, I took my father's side on the issue, no doubt for the selfish reason that I wanted to escape the constraints on behaviour that good manners imposed, but increasingly I think my mother was right. First, I do not believe that the human heart, undisciplined by rules and conventions, is good: on the contrary, the default setting, to use a computer analogy, is to savagery and selfishness. Second, it is unreasonable to demand of mannerliness that it should make people good in a deeper sense. Manners are the oil, not the engine, of moral conduct.

But if my mother won the battle for my mind, my father won the battle in the social sense: there can be little doubt that it is his view that has prevailed.

Being spontaneous and expressing oneself (regardless of content) is much more highly prized nowadays than obedience to a supposedly stuffy code laid down by convention or tradition. Unhappily, liberation from convention has not resulted in the emergence of man's natural beauty, but something altogether more Hobbesian and less attractive.

How was the victory over manners achieved? How were the British liberated from the need to behave towards each other with a reasonable degree of courtesy, a courtesy upon which - as George Orwell noted - foreign visitors often remarked?

First, the middle classes were persuaded by intellectuals for much of the century that an economy is a zero-sum game, and that they were prosperous because others were poor. Moreover, they were the bearers of a thoroughly undemocratic and elitist culture. This naturally made them feel guilty about their own privileged position (I was recently told by a colleague of mine how guilty he felt that, unlike so many of his patients, he had no financial worries whatever - as if, after half a lifetime of study and hard work, he ought still to have such worries, as if his patients had financial worries precisely because he had none).

From guilt, the middle classes soon passed to self-hatred. ("How beastly the bourgeois is!" exclaimed D H Lawrence, no mean social climber himself.) Those things they had previously valued they now found hateful: self-restraint, formality, decorum, dignity, fortitude and gentlemanliness. These became the objects of satire and derision: but, needless to say, many if not all of these qualities are required if people are to behave in a mannerly fashion.

A new model of how to behave was required. Where to look for it but the proletariat? Not the actual working class, but the imagined noble savage working class, which swore and fought, never minded its p's and q's and spoke its mind fearlessly, four-letter words and all. The middle classes imagined that working-class life was one long, drunken brawl. Here was authenticity rather than artificiality. And so, by behaving as if in a drunken brawl without necessarily being drunk, the middle classes could redeem themselves from the original sin of having been born privileged, or at least with no disadvantages.

The trouble is that it is easier to behave boorishly than with good manners, and what started as a pose became a habit and now has become, finally, a way of life.

It will not be easy to return to mannerliness, precisely because it never occurs to the young, middle-class women who put their feet up on the chair in my office to behave in any other way. The question of manners simply does not arise in their minds.

And so the British, from having been among the best-mannered people, have become in a few short decades among the worst. (I know of two nations whose manners are worse, but politeness requires that I do not name them.)

Alas, mannerliness has come to be associated in British minds with illicit wealth and elitism, and outward polish with inward depravity. They therefore seek to prove the purity of their hearts by the vileness of their behaviour.

That mannerliness is necessarily elitist and associated with wealth is the sheerest nonsense. Perhaps the best-mannered people I ever met were Tanzanian. Tanzania is always cited as one of the poorest countries in the world, but I encountered less rudeness there in three-and-a-half years than I generally encounter in half an hour at work in England. Indeed, I cannot recall a single incident of rudeness while I was there (except on my part), not even from the country's irritating officialdom.

Nor could it be said that the mannerliness of the Tanzanians resulted from the perfection of their country's political arrangements. Where I lived, everyone was thin, except for the party member, who was fat. Corruption was rife and injustice flagrant. But in day-to-day interactions, I found the Tanzanians to be possessed of the most beautiful manners.

When I look around me in Britain, I see nothing but boorishness and vulgarity, rejoicing in their triumph. The contrast with other nations is startling. Good manners are compatible with vice as bad manners are compatible with virtue; but when bad manners become general, the rule rather than the exception, daily life - no matter how prosperous - is a torment.