Who should ask the questions?

The problem for the Prime Minister is how to manage this new wider inquiry. President Bush will be able to ensure that his does not report until after the election later this year. His is to be a bipartisan group, who will have a great deal of material to investigate.

While Tony Blair might be attracted to the idea of a judicial inquiry, Lord Hutton has probably made that much more politically difficult. Rightly or wrongly, people are currently rather less sure of the balance shown by judges when they adjudicate on evidence outside their normal experience. There are committees in Parliament which could take on the task. The Intelligence and Security Committee has the access and background knowledge to do a good job.

However, it answers directly to the Prime Minister rather than to Parliament. The Foreign Affairs Select Committee answers to Parliament, but is both weaker and less expert in this field. In either case, it would be difficult to see how parliamentarians could afford to spend the time to take all the evidence and devote themselves to an objective, reasonably speedy and widely accepted inquiry.

Perhaps the time has come to form a new panel for such a vital national exercise. Lessons need to be learned from this debacle. Our intelligence services are vital to our national security. We need to trust them. We face dangers from terrorists, from poorly governed states, from the spread of powerful new weapons and from international crime.

Intelligence is our first line of defence. An inquiry would therefore be more about rebuilding national trust than finding scapegoats. It would inevitably need to be partly in private as some intelligence techniques cannot be revealed without damage to our interests. The panel would need to be recognised as independent of government, with no axe to grind, but with a reputation for integrity. It would need to contain members who were familiar with the workings of the various agencies involved.

All of this is a tall order. The leader of the panel would be the key appointment. Chris Patten might be seen as now sufficiently apolitical and objective. George Robertson has returned from Nato, and is distant from the government these days. Michael Quinlan, a former senior civil servant, would be less well known to the public, but fits the criteria of experience and integrity. It will be important to avoid past spymasters, who, however unfairly, will be open to accusations of looking after their old organisations. Any inquiry will also need to work closely with the US investigation, and this may need even greater diplomatic skills.

The war in Iraq is proving to be one of the great events of the new century. How we learn the lessons from this intervention will shape our security for years ahead. We had better get it right.

Sir Tim Garden is visiting professor at the Centre for Defence Studies, King's College London, and a former assistant chief of the UK defence staff.