Anne Penketh: So why was Dr Kelly so evasive in his evidence?

It is troubling that David Kelly lied to MPs about the conversations he held with journalists that led to Downing Street being accused of "sexing up" the evidence that led to Britain joining the US war on Iraq.

This emerged on the third day of the Hutton inquiry, which is now getting to grips with its mandate of discovering why the country's leading biological expert ended his life after being identified as the source of the BBC's accusations.

So now a whole new array of questions looms for Lord Hutton: did Dr Kelly take his own life because he lied to the committee? And why did this honest professional scientist lie?

The pressure on the scientist from his employers in the Ministry of Defence can only be imagined. But, so far, the Hutton inquiry has not attempted to establish the level of threats that were made against him once his name was circulated to the press.

He had been marched into the televisual glare of the Foreign Affairs Select Committee. Was he groomed on what to tell the MPs, or did he act on his own initiative?

Dr Kelly talked to journalists. He was even supposed to talk to journalists, as the MoD's personnel director, Richard Hatfield, recognised on Monday.

But the ministry drew the line when Dr Kelly ventured beyond his brief of "providing technical information" on an unattributable basis.

But did Dr Kelly really stray so far? His chat with the Newsnight reporter Susan Watts, in which the expert is relaxed and informative, certainly doesn't make him sound like a whistleblower, or even a man with an axe to grind against the Government.

Here is the cool professional still seeking to set a journalist straight about the insertion of the controversial claim that Iraq could deploy biological or chemical weapons within 45 minutes: "I don't think they're being wilfully dishonest," he says of Downing Street. "They just think that's the way the public will appreciate it best. I'm sure you have the same problem as a journalist, don't you?"

On the day of his conversation with Ms Watts, which took place on the day after Andrew Gilligan first broadcast his explosive charge, Dr Kelly even seems to be revelling in the attention.

He mentions that he had spoken to another BBC correspondent, Gavin Hewitt, earlier in the day - something which he will later tell MPs that he cannot recall doing.

He even laughs when asked by Ms Watts whether he has been "getting much flak" about the Gilligan story, because he was speaking to her from New York. "They wouldn't think it was me, I don't think. Maybe they would, maybe not."

But how different his state of mind must have been on 18 July, when he took his final walk into the countryside around his Oxfordshire home - the same day that Mr Gilligan was to face the McCarthyite atmosphere of the Foreign Affairs Select Committee. Dr Kelly must have feared that Mr Gilligan risked "outing" him as the main source for his story - wrongly, it turns out.

The MoD has serious questions to answer about how it dealt with Dr Kelly in the aftermath of 29 May, when Mr Gilligan's first charges were laid on the Today programme. Was this man facing his career in ruins, his security clearance withdrawn, for suggesting that the Government exaggerated the threat to UK security from Iraqi weapons of mass destruction?

This countryhas legislation that prevents "whistleblowers" from facing the sack or disciplinary action if they raise an issue of public concern. This is clearly the case with Dr Kelly.

Why was his anonymity not better protected by his employers? Should this legislation not have been invoked in his case before he was hounded to the grave?