It has happened already in Ireland, and I cannot wait for it to occur in Penrith - the alleged centre of anti-boat people prejudice. In Ireland there have already been two cases in which someone noticed a blond, blue-eyed child in the family of some Roma, and, thinking the little one did not much resemble the parents, got straight in touch with the Garda, out of general busybodiness. The Garda, of course, swooped with all of the alacrity that they failed to demonstrate over real child abuse and the child was confiscated as a precaution by the social worker establishment, with the onus, more or less, on the Roma to prove the child is theirs.

But then DNA tests satisfied the courts (damn) that each child really was the child of the Roma parents.

Ireland's Justice Minister Allan Shatter - perhaps a relative of Queensland's attorney-general - was not apologising for the implementation of the guilty-until-proven-innocent principle that applies to some classes of Irish crime but not others. Shatter said the police had acted in good faith in removing the children from their families.

''The law provides clear powers for An Garda Siochana where it is believed that a child may be in danger,'' he said. ''The Health Service Executive and the courts are involved in making the appropriate decisions.

''Urgent procedures are available to ensure that the safety of a child can be assured while necessary inquiries are being made. While such procedures can be understandably distressing for parents, the reality is that not invoking the procedures can involve taking a risk with the safety of a child if you don't act on the basis of the information that is available at the time.''

One cannot be too careful. This is just the right sort of approach. I urge all right-thinking Canberra families to ring the police immediately if there is any reason, even a mischievous one, to think that there is any sort of physical difference between any adult and any adjacent child. Focus on blond babies, I suggest, because we all know it is Aryans who matter most.

One might be stopping an abduction, a case of paedophilia, or perhaps some effort by a Jewish person to cut up a good Christian child for Satanic ceremonies. This ''blood libel'' against the Jews is closely associated with the idea that children are stolen by passing Gypsies, and if we are to panic we might all well go the whole hog, so to speak. While there is absolutely no evidence of Jews or Gypsies actually doing this over, say, the past 5000 years, that many right-minded bigots think they have, or might, ought to be enough to keep police and the social worker establishment on their mettle.

Prejudice against the Jews is now almost unfashionable, unless masked by antipathy to Israel and condemnation of its policies towards Palestinians. But prejudice against Roma, or Gypsies, has hardly abated since World War II and is still almost official policy in many parts of Europe. For most of the past millennium, Christians persecuted them almost as much as Jews. Nazis exterminated perhaps a million.

The Swiss removed Roma children from their parents, in somewhat the same way Australian welfare authorities ''rescued'' part-Aboriginal children, until the 1970s. To this day nations such as France and Italy are aggressive in deporting Roma. They are condemned for begging, stealing or otherwise behaving as members of a nomadic underclass, and for failing to assimilate, and are harried and moved on wherever they stop.

They are the absolute despair of middle-class social workers, who know best for everyone, and have a lamentable habit of being suspicious of policemen, council inspectors and clergymen. They have few defenders, particularly in countries with long histories of bigotry, demagogic politicians and scapegoat-seekers.

What tends to particularly distinguish modern popular prejudice and hysteria against Roma - as opposed to other ''aliens'' such as boat people, Aborigines, Muslims, Tasmanians and so on - has tended to be the ready association of public officialdom with those local outbreaks of hysteria that lead to pogroms.

It is never hard to see a Pauline Hanson or a Scott Morrison panicking whenever some apparent stranger is in our midst, but they are not usually accompanied by hordes of policemen, welfare officers or people in white gowns. It is never hard to get reptiles of the press to feed fuel into the fire, but otherwise uncommon to find usually sober journalists, academics and liberal people thinking this provides an opportunity to retail a lot of anecdotage and supposition about international child slavery, or traffic in human beings or body parts, or other tosh supposedly associated with Gypsies.

We are, in fact, a little short on actual cases of Gypsy abductions of children: I do not believe that one is documented. I have heard of poor, starving or perhaps wicked people selling children, but never Roma. That has not stopped the innuendo in reports for more than a week.

Yet I have often enough myself used the phrase ''gone with a passing Gypsy'' and my family has long had jokes about the substitution by trolls of their miserable, snarling, snivelling babies for our own happy gurgling infants.

Mythology and fairytales about child abduction of this sort - whether featuring trolls, Jews or Roma - reflects deep-seated and fundamental anxieties about separation and abandonment that probably go back to the Black Death in Europe.

That was, of course, just the time to blame anything unusual, including death or disease, on the presence or supposed customs, or alleged sins, of strangers. Hundreds of thousands of Jews and Gypsies have died for local panic about such matters. It is about time it stopped, even in Greece and Ireland - two supposed cradles of civilisation.

In the meantime, I await with interest the discovery that many Aboriginal children of the central deserts among, say, the Pitjantjatjara, Pintupi, Warlpiri and Arrernte are blond and blue-eyed, particularly up to about age 10. From among their parents, grandparents and great-grandparents came many of the stolen people.

But then we realised that stealing them on the basis of their being Aboriginal was wrong and apologised. Now, instead, we are ''removing'' them, and at a far greater proportional rate, on the basis they are neglected, possibly abused or not attending school. This is apparently for their own good, even if little objective good has come of it.

It might be better for general white morale, apparently the primary policy principle, if henceforth we seized these protectively just in case they have been abducted.

''Kill them all,'' as some Christian bishop said when ordering the massacre of 20,000 civilians, including children, at Beziers 804 years ago. ''God will recognise his own.''