I have just seen the results of a Christies Care survey showing that one in eight adults had not seen their parents for a year or more. Coincidentally, I have just been given the second volume of David Kynaston's history of modern Britain, Family Britain, 1951-1957: Tales of a New Jerusalem, in which he recreates the story of ordinary life against the background of contemporary events. It is a totally fascinating book. The children who were being born, in such numbers, in 1951, the year when this volume begins, are the very adults who are now, in such numbers, losing touch with their aged parents.

In 1951, we were still rejoicing in the end of rationing (my first child, born in 1950, and my second, born in 1952, were issued with ration books, but that was the end of it), the National Health Service, new schools, student grants… everything, in fact, to make us feel that the future was secure. No wonder so many of us cheerfully embarked on large families. It appals me to think how many of those families have now irrevocably come to pieces. Yet it is not at all surprising, if we look at it not from the sunny, nostalgic heights of the 1950s, but from the dismal, swampy, treacherous ground of today. We are, too many of us, too old. What is to happen to the very aged is becoming a national obsession and few of those aged want to turn to their children for help.

Nor is it possible for them to do so. While we, as young or middle-aged grown-ups, were mostly busy, we were somehow less frantically pressed for time, even if we had both families and jobs. Nor, I think, were we so pressed for cash, at least among the middle classes. Indeed, I am amazed by how extravagant I was, even with five children. I used to go on frivolous trips to London to buy clothes, for example, in the new Mary Quant shop in Knightsbridge, and there were lots of parties at which to show them off.

But it is not merely that people are too busy or too poor or even too geographically remote to keep in touch. In fact, the same survey found that the average distance between parents and grown-up children was 66 miles, a surprisingly low figure if you take into account those who live and work more than 300 miles away, not an insurmountable obstacle these days. Something else has changed.

I don't suppose there is anyone now middle aged who has not gone through a time of intense hostility to their parents. One of my children, my eldest son, seemed to become an adult at the age of about six, and, whatever his inner feelings, he never displayed them and quite genuinely seemed to enjoy conversation with his parents, and golf or cricket with his father, music with his mother. I know that is rare and that we were lucky. For the rest, there were bad times, sometimes inducing despair on both sides of the conflict, and certainly a breakdown in communication. But mercifully, those times were comparatively short (though they seemed endless), and now I live in a family that is perhaps closer than ever before, where it is inconceivable that any member should fall out of touch with another, by visits, telephone conversations or email.

Nevertheless I, like most of my contemporaries, cannot contemplate dependence on my children. I have never really faced the role-reversal involved. I still think of myself, quite unrealistically, as the protector, the provider, the one who is ultimately responsible. In consequence, I am as much obsessed with what is to become of me as the rest of my generation and in conversation we revert regularly to the problem.

What saddens me is that there seem to be many people who take their adolescent loathing of their family too seriously. They never get over it. They suffer from what used to be called fixed adolescence. I don't deny that these ancient battles are sometimes difficult to forget. In 1956, we bought a large house in North Oxford to accommodate my mother-in-law, recently widowed, in what was to be separate accommodation. When we moved in, the alterations designed to make it so were not finished and for two long traumatic months we had to share the same sitting room.

It was the time of the Suez crisis. My brother, a member of the then Foreign Office, was between postings and having come from Yugoslavia, was in London and was asked to be spokesman for the government for BBC television, an offer that he refused, being deeply hostile to Eden's policy. This story somehow reached the Daily Telegraph, my mother-in-law's preferred reading, and she gave Geoffrey solemn warnings against me and "my set". My brother was a communist. Why else would he have been in Yugoslavia? Why else did he and his wife speak fluent Russian? Why else did we oppose Conservative policy?

Geoffrey reverted to adolescence before my very eyes. But still we got over it, and benefited hugely, as did our children, from having Granny always in the house. Of course, the alienation of children from parents may not be the fault of the children. There are numerous ways that parents can behave badly to their children even when childhood is long past and there are certainly children who are so badly treated over the years that they cannot be expected to want anything other than estrangement.

All the same, it is sad to think of missing the intense pleasure of being on equal terms with one's own children, reflecting that you are responsible for the very existence of these funny, clever, amiable adults into whose houses you can go and whom you welcome into yours.

Well, you may say, I am lucky, but so are most of the people I know. We are the other seven of the one in eight. Nevertheless, there is an enormous and so far intractable problem in the relation between the generations, the old and the middle aged. Society, that is, institutional society, undoubtedly unfairly discriminates against the old (and being old seems to start at the age of about 58, from which time it is almost impossible to get a job, if you have been made redundant through no fault of your own).

There are far too many stories of old people being denied treatment by the NHS, or given only cursory and inadequate medical examinations, or being fobbed off with the suggestion that they must expect this pain when they get old, they can't expect to see or hear or walk up hills at their age. Often, they do not get treatment that would make a huge difference to their enjoyment of life. Some of these institutional attitudes may rub off on to the children of aged parents.

But this is not the real problem. The true horror of old age is dementia. How many of those whose children are not in touch are demented? This the statistics do not tell us. Yet society still takes it for granted that the children, especially the daughters, of parents with dementia will sacrifice their careers, their pleasures, their freedom to look after their parents. Some of those who do not visit or telephone or write may be seeking to avoid facing what would be for them virtually an end of their enjoyable life. For this I cannot blame them.