They were a little ahead of me. He was bigger, probably about nine years old, she was small, maybe six. He was dragging her along, pulling her arm and she was crying. I intervened and he turned on me. 'She's my sister,' he said, as if, like a toy car, that implied ownership and the right to treat her in any way he chose. I have thought a lot about those two recently, and also about the two kids who took their young brother to my children's school and then clobbered him across the side of the head because he pulled away and nearly ran in front of a car.

It is common, where I live, to see older children escorting younger ones to school. But because they are children they lack patience and self-control and quite often hit out at their charges. Yet they are surprised, even indignant, that I feel I have any right to interfere. They do not look to adults for guidance or protection and they clearly do not expect an unknown woman to show any interest in their behaviour.

Judging by the evidence in the Jamie Bulger case, most adults feel the same way. The shoppers in Bootle that day did not march up to the two urchins they saw with Jamie and demand to know what they were doing although many felt uneasy. Few can explain why they hung back but I suspect they believe, just as the children did, that they had no right to interfere. We have all been told the greatest risk to our children comes from strangers. To those we do not yet know we are all strangers and, as such, have lost the right to care about other people's children.

Last Wednesday the Home Office added another plank to the wall with which we seal our children off from the potential help of our fellow citizens. It began distributing a video, The Think Bubble, to schools. Teachers and police liaison officers will use it to teach four- to seven-year-olds to be wary not only of strangers who may do them harm, but also of their parents' friends, who might ask for a cuddle. Of course, they have taken on board the fact that most sexual abuse occurs with so-called friends.

So what are children to think? To whom should they turn for help? If we are creating a society in which even the smallest children cannot expect help from others, the obvious answer is that they must take care of themselves.

And what are parents to do if all adults are suspect and they can trust nobody to help them with the job of caring for their children? Probably the most chilling quote of the week came from a young mother interviewed for the Today Programme on Radio 4 who said that she now is worried if a friend takes 'too much interest in my little girl'.

It is virtually impossible for a hard- pressed parent to be available to his or her children every minute. If other adults are dangerous, another way round the problem must be found. Children will be left alone while the parent pops out to the shops, left in the care of older siblings, and as soon as they seem old enough, left to fend for themselves.

For a child under five an unsupervised home is a death trap. In this age group accidents in the home account for more deaths than any other cause. For older children most fatal accidents occur in the street. The Child Accident Prevention Trust says a child under 12 cannot judge traffic well enough to take him or her safely across a busy street, let alone negotiate the same journey holding the hand of an excitable younger child. In 1990, four children between five and ten were murdered; in that same year, 81 child pedestrians in the same age group were killed on the roads. How many died because they were more afraid to seek the help of an adult stranger than they were of the traffic?

The two boys who took Jamie away were children. They needed a stern but friendly stranger who would stop them and ask their names. They should have expected intervention when they mistreated him in public. The most horrifying aspect of this case was the statements by passers-by who did nothing because they assumed the boys they saw were Jamie's brothers. They, too, believed a family member is a possession to be kicked at will.

The greatest danger our children face is not the evil intentions of adults, it is their indifference.