I was struck by the similarity of displays on many of their office pinboards. "That's where we hang our conscience," said an agency photographer.

There were photographs of dismembered bodies, of soldiers holding up severed ears and testicles and of the actual moments of torture. There were men and women being beaten to death, and drowned, and humiliated in stomach-turning ways. On one photograph was a stick-on balloon above the torturer's head, which said: "That'll teach you to talk to the press."

The question came up whenever visitors caught sight of these pictures: why had they not been published? A standard response was that newspapers would not publish them, because their readers would not accept them. And to publish them, without an explanation of the wider circumstances of the war, was to "sensationalize".

At first, I accepted the apparent logic of this; atrocities and torture by "us" were surely aberrations by definition. My education thereafter was rapid; for this rationale did not explain the growing evidence of civilians killed, maimed, made homeless and sent mad by "anti-personnel" bombs dropped on villages, schools and hospitals.

Nor did it explain the children burned to a bubbling pulp by something called napalm, or farmers hunted in helicopter "turkey shoots", or a "suspect" tortured to death with a rope around his neck, dragged behind a jeep filled with doped and laughing American soldiers.

Nor did it explain why so many soldiers kept human parts in their wallets and special forces officers who kept human skulls in their huts, inscribed with the words: "One down, a million to go."

Philip Jones Griffiths, the great Welsh freelance photographer with whom I worked in Vietnam, tried to stop an American officer blowing to bits a huddled group of women and children.

"They're civilians," he yelled.

"What civilians?" came the reply.

Jones Griffiths and others tried to interest the news agencies in pictures that told the truth about that atrocious war. The response often was: "So what's new?"

The difference today is that the truth of the equally atrocious Anglo-American invasion of Iraq is news. Moreover, leaked Pentagon documents make clear that torture is widespread in Iraq. Amnesty International says it is "systematic".

And yet, we have only begun to identify the unspeakable element that unites the invasion of Vietnam with the invasion of Iraq. This element draws together most colonial occupations, no matter where or when. It is the essence of imperialism, a word only now being restored to our dictionaries. It is racism.

In Kenya in the 1950s, the British slaughtered an estimated 10,000 Kenyans and ran concentration camps where the conditions were so harsh that 402 inmates died in just one month. Torture, flogging and abuse of women and children were commonplace. "The special prisons," wrote the imperial historian V.G. Kiernan, "were probably as bad as any similar Nazi or Japanese establishments."

None of this was news at the time. The "Mau Mau terror" was reported and perceived one way: as "demonic" black against white. The racist message was clear, but "our" racism was never mentioned.

In Kenya, as in the failed American attempt to colonize Vietnam, as in Iraq, racism fuelled the indiscriminate attacks on civilians, and the torture. When they arrived in Vietnam, the Americans regarded the Vietnamese as human lice. They called them "gooks" and "dinks" and "slopes" and they killed them in industrial quantities, just as they had slaughtered the Native Americans; indeed, Vietnam was known as "Indian country".

In Iraq, nothing has changed.

In boasting openly about killing "rats in their nest," US marine snipers, who in Falluja shot dead women, children and the elderly, just as German snipers shot dead Jews in the Warsaw Ghetto, were reflecting the racism of their leaders.

Paul W Wolfowitz, the Deputy Defense Secretary who is said to be the architect of the invasion of Iraq, has spoken of "snakes" and "draining the swamps" in the "uncivilized parts of the world".

Much of this modern imperial racism was invented in Britain. Listen to its subtle expressions, as British spokesmen find their weasel words in refusing to acknowledge the numbers of Iraqis killed or maimed by their cluster bombs, whose actual effects are no different from the effects of suicide bombers; they are weapons of terrorism. Listen to Adam Ingram, the armed forces minister, drone on in parliament, refusing to say how many innocent people are the victims of his government.

In Vietnam, the shooting of women and their babies in the village of My Lai was called an "American Tragedy" by Newsweek magazine. Be prepared for more of the "our tragedy" line that invites sympathy for the invaders.

The Americans left three million dead in Vietnam and a once bountiful land devastated and poisoned with the effects of the chemical weapons they used. While American politicians and Hollywood wrung their hands over GIs missing-in-action, who gave a damn for the Vietnamese?

In Iraq, nothing has changed.

By the most conservative estimates, the Americans and the British have left 11,000 civilians dead. Include Iraqi conscripts, and the figure quadruples.

"We count every screw driver, but we don't count dead Iraqis," said an American officer during the 1991 slaughter. Adam Ingram may not be as literate, but the dishonouring of human life is the same.

Yes, the atrocities and torture are news now. But how are they news? asks the writer Ahdaf Soueif. A BBC news presenter describes the torture pictures as "merely mementoes". Yes, of course: just like the human parts kept in wallets in Vietnam.

BBC commentators -- always the best measure of the British establishment thinking on its feet -- remind us that the torturing, humiliating of soldiers "does not compare with Saddam Hussein's systematic tortures and executions". Saddam, noted Ahdaf Soueif, "is now the moral compass of the West".

We cannot give back Iraqi lives extinguished or ruined by those acting in our name. At the very least, we must demand that those responsible for this epic crime get out of Iraq now and that we have an opportunity to prosecute and judge them, and to make amends to the Iraqi people. Anything less disqualifies "us" as civilized.