Five years after the American and British governments launched the most ill-conceived and fundamentally flawed war of the modern era; the British Prime Minister Gordon Brown has finally promised a full-scale inquiry into the war.

Although the Labour government has held four political “Inquiries” before, this is the first time that a British Prime Minister has acknowledged that a full public inquiry is necessary to unpick the disastrous lessons of the conflict. His admission is in direct contrast to Tony Blair who said in 2005: “We have had inquiry after inquiry we do not need to go back over this again and again.”

So what would a public inquiry find? It would have to hear evidence as to whether the war was legal, and would most likely conclude it was not. One key witness would be Elizabeth Wilmshurst, who was deputy legal adviser to the British Foreign Office before the war.

Wilmshurst resigned the day the war started. She argued that without a second resolution at the UN Security Council authorizing force, the war was illegal. Her resignation letter said she could not “in conscience go along with advice” of then Attorney General, Lord Goldsmith, as he changed his view to try and fudge the facts to say war was justified.

Any inquiry would also have to hear from Jonathan Powell, Tony Blair’s former chief of staff, who just last weekend week-end admitted the British and US governments had seriously underestimated the scale of any post-invasion task.

Powell said: “The trouble with Iraq is we were kind of preparing for the wrong sort of aftermath. We made lots of preparations for humanitarian disaster, for the lack of water, of all that kind of thing, and what we hadn’t in my view thought through was the long-term nature of this. I don’t think any of us had thought through this much bigger question of what we are dealing with.”

The truth is that the Blair and Bush governments were too preoccupied to try and spin the case for war to understand its full consequences. The falsehoods of Britain and America’s “dirty dossiers” purporting to show weapons of mass destruction have been long exposed. But in a retreat of another justification for war, the Pentagon finally acknowledged last week that a review of more than 600,000 captured Iraqi documents showed "no evidence that Saddam Hussein's regime had any operational links with Osama bin Laden's al-Qa'ida terrorist network".

The reality is one we have known all along. Al Qaeda never had a presence in Iraq, until the chaos created by the war allowed it to have one. Moreover, as the US has got bogged down in Iraq, it has allowed Al Qaeda to re-establish itself in the tribal lands of Pakistan and Afghanistan.

Even the feeble justification for removing Saddam on humanitarian grounds, now, five years later, looks like a complete disaster. Let’s quickly look at the lethal legacy of the war five years on. Figures on the numbers killed vary depending on who you talk to, ranging from an estimated 90,000 by the Iraqi Body Count to 1.2 million by the British polling company Opinion Research Business.

Over 2.2 million Iraqis have fled the country, with an estimated two million internally displaced. Some 50,000 are said to be homeless in Baghdad alone. It is impossible to describe the scale of human suffering that hides behind each statistic. A generation of Iraqi children is growing up terrorized and traumatized, having witnessed or been subject to violence.

Each story is a human tragedy. “My children and I left my home in Anbar almost two years ago” thirty-eight year old Ruba told the Red Cross. “My husband had been killed right in front of us. I had to protect my children, so we fled the same night with nothing but some money. For me, there is no past and no future, only a horrible present.”

The Red Cross recently concluded that “five years after the outbreak of the war in Iraq, the humanitarian situation in most of the country remains among the most critical in the world. Because of the conflict, millions of Iraqis have insufficient access to clean water, sanitation and health care.”

For those providing services such as health care it can be perilous: Over 2,200 doctors and nurses have been killed, with over 250 kidnapped. For many it is too much: Some 20,000 of the 34,000 registered doctors in the country have left.

The average wage in Iraq – that is, if you can get a job, is now around $150 per month, yet many families are having to spend at least $50 just to get clean water.  Baghdad still struggles to get one hour of electricity per day.

To coincide with the fifth anniversary of the conflict, many media have undertaken different surveys of what life is like in Iraq. Given the appalling state of the country, an overtly optimistic picture was painted by a BBC poll that found that over 50% of Iraqis think their lives are “good.” Whilst this is a national figure, it masks the deep ethnic divisions with only 33% of Sunnis being “happy”, compared with 62% of Shias and 73% of Kurds.

This seems far too optimistic and is contradicted by other surveys and reports. For example, of the ten people interviewed for the Observer earlier this month, 3 people or 30 per cent, said they wished Saddam was still in power, another argued that the war had set Iraq back 50 years.

What the BBC and other surveys have shown is that Iraqis still rate security as the biggest problem for the country overall. Thabit is a Sunni who lives near Kirkuk. He says “before 2003 we only had to worry about not saying anything against the government. Now we can say all we want, but life is in continuous threat”. Another Iraqi, Amaal, a mother of six and teacher of biochemistry in Baghdad says: “It is true that some people are very poor in society, but I know many people who would prefer to live in poverty if they were given security.”

The US claims that the “surge” in American troops has had a dramatic effect on reducing the violence in Baghdad. They spout statistics to back this up. The number of sectarian attacks in Baghdad dropped from 2200 in December 2006 to 200 in November 2007. This, like most American military propaganda, has missed the point.

The reason that violence is fallen is that the city has now been effectively ethnically cleansed. Instisar is a Sunni accountant who lives in Baghdad. She says that in her street there are only three families left who lived there before the war. The rest have “emigrated or fled”. Ghaith Abdul-Ahad, an Iraqi photo-journalist has just returned from the city. Able to go to districts no western journalist can go, he says that Baghdad has been transformed into a city of walls. Some 20 miles of 12 foot concrete barriers now dissect this city keeping Sunni and Shia apart. Each neighborhood or district is controlled by different militia. “The people are more desperate than ever”, reports Ghaith Abdul-Ahad.

This post-apocalyptic hell is surely not what President Bush had in mind when he said in 2003: "Iraqi democracy will succeed - and that success will send forth the news, from Damascus to Teheran - that freedom can be the future of every nation."

For the Americans there is no end is sight, either: In 2008, there were more American troops in Iraq than during the invasion. Nearly 4000 American soldiers have been killed and 30,000 wounded. Over 16,000 American troops have deserted. The figure may well be higher, with many of the runaways quietly discharged. Britain may have lost far fewer soldiers – just 175 - but it has been forced to retreat out of the city of Basra and still cannot pull its soldiers out of the country.

The cost is not just in lives either. In 2003, US Defence Secretary said the cost of the war would be $60bn. To date, the US government has spent at least $500 billion on the war, with some estimates it is as high as $4 trillion. In the UK, an influential Commons Committee recently warned of a “surprising” 52 per cent increase in the cost of military action in Iraq to nearly £1.45bn, despite recent reductions in troop levels.

Gordon Brown has said of the public inquiry: "There is a need to learn all possible lessons from the military action in Iraq and its aftermath." The main lesson, according to Hans Blix the UN’s former weapons chief, is “that there are limitations to what you can achieve by military means.” But the British and Americans should have realized this before they invaded. As Robert Fisk, the award winning journalist wrote last week: “The only lesson we ever learn is that we never learn”. And we don’t need a public inquiry to tell us that.