Leading article: The crucial questions that the Iraq inquiry must answer

The panel has been selected. The terms of reference have been decided. The official documents have been lodged. And so now begins the real work of the independent inquiry into the invasion of Iraq: taking public testimony from the key figures involved.

Senior civil service officials, diplomats and military officers will be questioned by Sir John Chilcot's panel in the run up to Christmas. In the New Year it will be the turn of the politicians, including Tony Blair and Gordon Brown. Sir John says he hopes to produce his final report by the end of 2010. So will this be the final word on Britain's most controversial foreign policy entanglement since Suez? That is most unlikely. But it does not follow that this inquiry is destined to be a pointless exercise.

This newspaper would have preferred a full public inquiry into Britain's involvement in the Iraq war. And Sir John's civil service background (and the fact that his fellow panel members were handpicked by Downing Street) has raised suspicions that he will produce a report that may be unduly sympathetic to the Government.

Yet it need not be this way. For one thing, the inquiry has been given the authority to examine events going back to 2001, which allows the panel to get deep into the events leading up to the 2003 invasion. For another, Sir John has been given discretion to open hearings to the public, a freedom he has indicated that will be fully used. And Sir John has certainly been keen to emphasise the independence of his panel in recent days, explicitly pledging that there will be no "whitewash". These are positive signs.

But in the end, Sir John and his team will be judged on their success in getting answers to a number of crucial questions: What intelligence on the threat posed by Iraq did ministers see and was this evidence deliberately distorted in making the public case for war? Was the door prematurely shut on a diplomatic solution to the crisis?

How independent of Washington was British foreign policy? And what advice were ministers given over the legality of the invasion? Also requiring detailed investigation are issues over the planning for the invasion and the provision of equipment for troops.

There are those are argue that all the various inquiries relating to the invasion of Iraq in recent years have sufficiently answered such questions. Not so. The Hutton inquiry was charged with investigating the death of Dr David Kelly. The Butler inquiry was instructed to examine why public warnings about Saddam Hussein's supposed stockpiles of weapons of mass destruction were so wrong. Two investigations by House of Commons committees were similarly narrow. This is the first inquiry charged with considering the Iraq conflict in its entirety.

There remains a great deal to be clarified about how and why Britain ended up at war in Iraq. Indeed, new documents came to light this weekend suggesting that British preparations to invade Iraq began as early as February 2002.

We should be realistic. No matter what this inquiry ultimately produces, it is most unlikely to heal the wounds opened up by this most bitter of arguments; nor can it hope to satisfy all sides. Nevertheless Sir John and his team can usefully shed light on a matter of still overwhelming public importance, should they grasp the opportunity.