The Iraq inquiry opened yesterday. Its work may take years. It has a stupendous task: restoring the faith of the British people in their political system. For this it must outdo its predecessors and produce conclusions which are comprehensive and believable.  But with the best will in the world, the inquiry could all too easily ask – and answer – the wrong questions.

That risk is apparent from the leaked documents of military lessons learnt in the immediate aftermath of the conquest of Iraq. As recently reported, they tell a terrible story. Because Tony Blair’s commitment to the war had to be concealed, our forces in Iraq were denied the equipment and resources they needed, and, still more fatally, lacked planning and instructions for the occupation of Iraq.

This story will have deep resonance for our forces and their families – especially when the same kind of equipment and planning failures are  reported from Afghanistan. The inquiry must deal with it conclusively,  not just for Britain’s sake but also for the millions of Iraqi victims of violence and breakdown during the occupation.

But this is not the right place for the inquiry to begin. Before asking whether the government made proper plans for the war and occupation, the inquiry must decide whether it should have gone into this war in the first place. Was the war necessary and lawful? Was British participation essential and did it produce any benefit for our country? Even if judged a mistake, was it a reasonable decision for Tony Blair to make, in the light of what he knew at the time? Was he honest to the British people over its timing and motives and in the evidence and arguments he presented to justify it?

These are the key issues for the inquiry and only Tony Blair can resolve them. He is due to appear in February. His appearance may be brief and they must use it well, by asking penetrating questions. Here are some suggestions (and supplementaries) on important unresolved issues. The inquiry could and should compare Tony Blair’s responses to the evidence of other witnesses and that of written records.

1) When did you first learn of the Bush administration’s intention to invade Iraq and overthrow Saddam Hussein? What was your response?

2) The invasion of Iraq had many opponents in the United States, including senior military figures and members of the Bush administration. You had considerable influence over American opinion. Did you ever consider using this, either publicly or privately, in support of the war’s opponents?

3) Did Britain’s defence staff advise you at any time after 1997 that a pre-emptive war against Saddam Hussein was necessary or a high priority?

4) When did you first commit British military support to the Bush administration’s plans for Iraq? Did you attach any conditions to this? Did you consider alternative means of demonstrating military support (such as committing more troops to Afghanistan or relieving American garrisons in Europe or Korea)?

5) When were the first plans made to commit specific British units to an invasion of Iraq, and who was aware of them in your government?

6) Why did you think it necessary to issue the September dossier, to inform and influence public opinion on Iraq, at a time when Britain’s public policy was to secure the return of the UN weapons inspectors. This policy commanded almost universal support. Did you assume that the UN weapons inspectors would fail and that war was inevitable?

7) Did you receive any specific warning from defence or intelligence sources that Saddam Hussein was ready to supply WMD to Al-Qaeda? [This scenario was always far-fetched. Vicious dictators simply do not give away their deadliest weapons to people they do not control.]

8) Did you receive any information or analysis from any source to suggest, correctly, that Saddam Hussein had no WMD? [In his book The Way Of The World, the American Pulitzer Prize-winning author, Ron Suskind, presents a detailed narrative which suggests that Tony Blair received precisely such an analysis from MI6, and that he believed it and that he sent it to George W Bush in a last-minute bid to head off the war. The inquiry must examine this story. If true, it destroys almost everything that Tony Blair has ever said about Iraq].