The appalling rapist who made his two daughters pregnant 19 times in 28 years did not need to build an underground cell, like Josef Fritzl, in which to commit his crimes: he could rely, instead, on the thick walls of British reticence to hide the horror.

The “Gaffer”, as he called himself, moved home every six months, repeatedly relocating his family in isolated villages in the North. This man was a monster, but he had an acute understanding of how modern British society can sometimes fail to see the most glaring crimes.

Occasionally the man's neighbours became suspicious. Very occasionally, they asked questions. Mostly, they did not. In the end, it was the questioning of journalists that led to his arrest.

That he could keep his horrible secret for three decades is primarily the fault of the professionals - the social workers, the doctors and the police - but it was also a failure of society, grim proof of the anonymity that can found in even the smallest community.

When the Fritzl story broke, British commentators denounced the Austrian “culture of secrecy”, yet our own culture also ignores its darkest and secrets, often in the name of privacy.

“Minding your own business”, “keeping yourself to yourself”, “turning a blind eye” - these are not just British traits but organising principles of society. An Englishman's home is his castle, and what goes on behind its walls is regarded as no business of those in the castle next door.

In some ways, the British defence of privacy is an admirable quality. It makes us tolerant of newcomers, unwilling to pry and vigorous in defence of personal space. George Orwell's nightmare vision of state surveillance in Ninteen Eighty-Four addresses a peculiarly British fear of privacy invaded.

British politeness and reserve require the keeping of a distance. We agree with Robert Frost, “good fences make good neighbours”, and a thick leylandii hedge is better still. Government attempts to monitor individuals through identity cards; DNA databases and surveillance cameras meet staunch resistance.

The flip side of this defensive privacy is that it helps to create a society of strangers, one that values space and seclusion over human contact. So, far from loving our neighbours, we find it easier to pretend they are not there. We twitch our net curtains, tut and wonder what is going on across the road, but say little and do nothing.

The social anthropologist Sir Edmund Leach spoke of “the family with its narrow privacy and tawdry secrets”. In modern Britain, people are increasingly reluctant to take responsibility for those outside the immediate family circle; that circle, in turn, is regarded as a strictly private domain.

The “authorities” bear the heaviest responsibility for child protection, but in the past that role was shared with the rest of society. More than half of all complaints made to the London branch of the NSPCC in the 1880s came from neighbours who thought they had spotted evidence of abuse or neglect. The nosy neighbour was a busybody, and often a life-saver.

Welfare agencies report that individuals are increasingly reluctant to report their suspicions of child abuse for fear that a complaint may backfire, provoking retaliation or endangering the child further. That unwillingness to speak out is part of a wider breakdown in local social relations, creating communities in which individuals can get lost and entire families become invisible.

A recent study by the Young Foundation found that while people long for more “neighbourliness” in their lives, hectic and transient lifestyles increasingly preclude social intimacy. The mobility of modern life, the breakdown of extended families, longer working hours and home entertainment have all helped to isolate families and individuals from those living around them.

We imagine smaller rural communities to be closer-knit, but even here the opportunities to know the neighbours are steadily eroding, as the church, the Women's Institute and the social club disappear. The pub is now a restaurant; the front garden is more likely to be a car parking spot than a meeting place. The post office has gone the way of the sports club and the library. On average, people travel three and half miles to buy groceries, and 45 minutes to get to work.

Not long ago the Gaffer's crimes would not have been able to pass undetected under the natural radar of neighbourliness. Today we barely notice who comes and goes: according to one poll, fewer than one person in five across the UK is greeted by neighbours when moving into a new home.

This is the society that allowed the Gaffer to move from place to place with his battered, permanently pregnant daughters, without being noticed for what he was. According to the prosecution, there was “speculation and talk from the neighbours about the growing family and the lack of any other men”. But there is wide gap between gossip and action.

Perhaps the most telling remark in the horrific Baby P case came from a man who had lived for 20 years in the Haringey estate where the child was killed. “It is not a neighbourhood and we are not neighbours,” he said bleakly. “I know one or two people, good friends, but that's it.” No one would want to live in a society of snoopers and tattle-tales.

Nostalgia for some mythical Britain of community cohesion is pointless, and possibly unhealthy. Yet we seem, as a society, to have lost the balance between defending personal privacy and a community's duty to watch over its own most vulnerable members.

The two daughters of the unspeakable Gaffer dropped, tragically, through Britain's welfare net; but they also slipped through the net of neighbourly vigilance, a part of the social fabric that is harder to define, and far more difficult to mend.

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