I left the assessments staff just six months before the dreaded dossier was published. From what came out at the Hutton inquiry I could hardly recognise the organisation I had so recently worked for. Meetings with no minutes, an intelligence analytical group on a highly specialised subject which included unqualified officials in Downing Street but excluded the DIS's lifetime experts (like Dr Brian Jones), vague and unexplained bits of intelligence appearing in the dossier as gospel (notably the 45-minute claim), sloppy use of language, that weird "last call" for intelligence like Henry II raving about Thomas a' Becket - with "who will furnish me with the intelligence I need" substituted for "who will rid me of that turbulent priest".

I looked forward to Lord Hutton making some serious suggestions about how to keep the intelligence process free of political manipulation and analysts free from the preparation of propaganda dossiers. I thought he might help explain, too, why the intelligence community had been taken by surprise by the aftermath of victory in Iraq.

When the report came I was puzzled at first - serious people seemed to be taking it so seriously. And then everyone started to laugh. Some of the passages - particularly "the possibility cannot be completely ruled out that the desire of the prime minister ... may have subconsciously influenced ... members of the JIC ... consistent with the intelligence available to the JIC" are masterpieces of comic writing.

In two years as an intelligence officer, and four-and-a-half years as an analyst at the highest level, I never once heard the phrase "consistent with intelligence". It means nothing. I have often been asked whether I was sure that I had reviewed all the available intelligence or whether I was sure I was on the right track. But no one has ever asked me whether something was consistent with the intelligence. Intelligence is by its nature inconsistent. Very often the right answer, the answer closest to the truth, draws on just a small part of the material available to you because you have discounted the rest. It was consistent with the intelligence for the German high command to expect that the D-day landings were going to take place near Calais. Consistent - except that the intelligence was part of a deception operation.

But it has recently got even more embarrassing. The prime minister told the House of Commons that he was unaware at the time of the war debate that the 45-minute piece of intelligence referred only to battlefield rather than strategic weapons. Let me list just some of the procedures which must have been executed incorrectly to allow him to be kept in such a state of ignorance at such a crucial time on such a crucial matter when other members of his cabinet (Cook and Hoon) appear to have been in the know.

One: neither Cook nor Hoon saw fit to tell the prime minister, for whatever reason.

Two: the intelligence was not considered important or accurate enough to explain to him in detail - even though it appears in the September 24 dossier at least three times and in the prime minister's own foreword.

Three: Blair had to rely on verbal briefings from the JIC chairman and others, who told him about the 45 minutes bit of the intelligence but omitted to mention that it referred only to battlefield weapons, and neither the prime minister nor any of the brilliant young staff asked the obvious question.

Four: the original SIS report mentioned the 45-minute time, but made no attempt to distinguish between strategic and battlefield weapons - even though the service was aware that the report was about battlefield munitions.

Five: the prime minister's daily written intelligence brief from the Cabinet Office included the 45 minutes point but not the crucial distinction between battlefield and strategic weapons. And not a single member of the Cabinet Office assessments staff (the most brilliant intelligence analysts in the UK) spotted this or thought it important.

This is not the case of a few guardsmen out of step or a few trumpeters out of tune. This is like holding trooping the colour but forgetting to tell the Queen the correct date.

· Lieutenant Colonel Crispin Black worked for defence intelligence from 1994-96 and was on the intelligence assessment staff from 1999-2002