The summers were hotter than usual; and signs of social disintegration were everywhere. Crime was soaring; muggings were endemic; racial tension was high; recreational drug use was the urban norm.

Divorce rates were racing higher; abortions, extramarital and premarital sex had rarely been as casually available. Public transport brought its own hazards and threats: antisocial behaviour, drunks, graffiti, boorishness and murder made the Tube a legendary place to avoid.

Serial killers filled the news; occasional mini-riots broke out; every day you heard of a car broken into or a house burgled or a neighbour mugged. Schools seemed more like holding pens for hooligans than places of learning; universities were places where the aspiring elites learnt how to copulate and roll joints and argue that all forms of culture are equally valuable.

As national identity seemed to be fraying, the upper middle classes partied and chattered. And as wave after wave of new immigrants and asylum-seekers arrived, the very meaning of national identity began to come unglued. In the inner city, the ghettoes were full of gang violence; and the culture was seized by what elected officials called a “malaise”.

Ah, the New York City of the late 1970s. Sound familiar? To read the British press these days you’d think London in the new millennium was identical. Or Birmingham, Manchester and Glasgow for that matter.

You know the litany of the cultural declinists: the ubiquitous boorishness, the declining standards of public behaviour, the collapse of education, the fragility of the family, the cult of selfishness, vulgarity and hedonism that permeates public life. Some even managed to blame British “decadence” for the 7/7 bombings.

Here’s our own columnist Minette Marrin a fortnight ago: “One of the things that strikes me more, not less, forcibly as time has passed is the contempt that Muslim extremists feel for us. They despise us for our decadence, and I feel more and more forced to accept the painful truth that they have a point . . . Without proper discipline from parents, children can never develop self-discipline. And it is on self-discipline and self-restraint that a civilised society rests.”

You heard the same arguments 30 years ago in America. No one believed things could or would improve. Many conservatives assumed that the 1970s had all but ended civilised life, and that only a minor miracle could rescue the family from terminal decline as a social institution. Crime would merely spiral upward; ditto illegitimacy and divorce.

And then over the next few decades something surprising happened. The trends slowly faltered, reversed and improved with surprising speed. From a hellhole far deeper and more worrisome than even the most depressed Londoners could conjure today, New York emerged in only a couple of decades as a different place altogether.

These days, even in the terrifying wake of 9/11, New York City boasts record low crime rates, a solid economy, rising educational standards, less racial tension and lower and lower levels of illegitimacy and domestic violence. In fact, much of what was once an edgy, terrifying, almost gothic Gotham now seems bathed in a near-narcotic calm, a bourgeois suburban theme-park from midtown south. If you want a good investment, try buying some housing stock in Harlem — yes, Harlem — the latest piece of former ghetto to become an impending upscale urban oasis.

New York was one of the more exceptional points of light in a two-decade upswing of social improvement. But much of America experienced the same beneficent trends: the reconstitution of the family, the decline of illegitimate births, the collapse of crime, the reinvention and expansion of work.

The revival baffled the pessimists. The social collapse of the “decadent” West had been hailed regularly for years — and the era after the sexual revolution seemed like the final twist downward. The younger generation had been going to the lower recesses of post-everything nihilism since Elvis.

Many of those worries were indeed legitimate. The boom in abortion, illegitimacy and divorce in the late 1960s to the mid-1980s undoubtedly hurt a generation of offspring. Even today it’s hard for many Americans in my generation to see pictures of their parents rolling about in the mud at Woodstock without a twinge of embarrassment and a wave of bafflement.