Finally its over - after six years since the invasion of Iraq our troops are finally coming home. With the Defence Secretary admitting at the handover ceremony that there needs to be a 'proper investigation' into the failings of the mission suggests that our troops are not departing Iraq with their heads held high. 'Operation Telic' has been a disaster, the blame for which falls firmly on the shoulders of Whitehall and not the British military.

General Robin Brimms, commander of British Division which invaded the south of Iraq in 2003, recently recalled the day in April 2003 when the war fighting ended and peace keeping/ nation building should have began. He realised there was no plan, no money, no support available to start the reconstruction, develop local governance and build on the jubilation of a nation that has just been liberated from a despicable dictator.

And so without a plan, and with no one filling the power vacuum, looting began. This led to the growth of organised gangs and then into armed militias. Basra became unlawful, with whole districts ruled by different armed, extremist groups who closed all bars and barber shops, punished women who did not wear a veil, and murdered anyone who criticised or question their authority. British forces could no longer provide any level of security and were now seen as occupiers rather than liberators. In August 2007 the city was abandoned and the British retreated to the fortified confines of the airport.

Exasperated by the lawless in the south, the Iraqi Prime Minister sent in 30,000 troops supported by US forces to flush out all the militias in Basra. The attack called 'Charge of the Knights' killed hundreds of fighters, while many thousands fled to Iran. Other than providing some logistical support, Britain played no role and 4,000 troops remained in their base at Basra airport.

Some say today that Iraq is improving. Al Quada is no longer present; the number of terrorist attacks is falling; and there is no need for such a large allied presence. This is all true. But Al Quada was never in the country in the first place. It was only by exploiting a power vacuum that the west created in the aftermath of the invasion which allowed them in.

The question is, should it really have taken six years, 179 British deaths and £8.5bn to bring relative peace to an area the size of Surrey? And when the decision to invade was made, was it really our objective to hand over our area of responsibility, not to the Iraqis but to US forces? The answers lie in Whitehall, especially at the Department for International Development, where thanks to Clare Short, the Secretary of State at the time, refused to participate in any pre-invasion planning.

I never agreed with the invasion in the first place, but failure of Whitehall to support our troops in post invasion planning allowed the entire operation to go down hill and last years longer than it needed to. There are lessons to be leant which could be drawn out with a full inquiry. Until then we are on course to repeat the same mistakes again. This time in Afghanistan.