The pioneering weapons inspector who uncovered Saddam Hussein’s secret anthrax programme was incensed at his treatment by a committee of MPs and frustrated that his own evidence to them had been flawed.

Dr Kelly apparently found it impossible to live with his inner torment.

At 3pm on Thursday he left his house, saying he was going for a walk. Paul Weaver, a farmer, spotted the scientist on a footpath more than a mile from his home. The only oddity was why the keen rambler was alone, instead of walking with his wife and daughters as usual.

Dr Kelly headed through wheatfields to a wood on Harrowdown Hill near Faringdon, about five miles from his home. His family alerted police that he was missing at 11.45pm and, after an all-night search using a helicopter, a body was found at 9.30am.

Dr Kelly seems to have been frustrated that his evidence to the Foreign Affairs Select Committee may have inadvertently played down his role as a source for Andrew Gilligan’s BBC allegations.

“His wonderful semantic precision let him down during that meeting,” Tom Mangold, the former Panorama reporter and a friend of Dr Kelly, told The Times. “He said he didn’t think he was Andrew Gilligan’s one source. He should have said he didn’t recognise part of Andrew Gilligan’s submission.”

Dr Kelly, 59, a married father of three, had vainly hoped that his appearance before the committee would be cathartic. “For a man like David Kelly, who had worked with intelligence services around the world, to sit there and be told he was a prat and a fall guy was dreadful,” Mr Mangold said.

“He was an honourable, dedicated man. He volunteered this information to his employers at the MoD in the knowledge that he would probably go before a committee. He did not realise the committee would treat him with such contempt.”

Mr Mangold spoke to Dr Kelly’s wife, Janice, shortly after the body was discovered by the police at a beauty spot about a mile from their Oxfordshire home yesterday morning. “She said he was very upset by what had occurred on the committee and very angry,” Mr Mangold said. “Importantly, she did not use the word ‘depressed’. He was the bane of Saddam Hussein, who personally wanted him expelled from the country because he knew where ‘the bodies were buried’.”

Born in the Rhondda Valley, Dr Kelly’s first love was science. He studied for a BSc in bacteriology at Leeds University, took his doctorate at Oxford, then joined the Oxford Institute of Microbiology as a biological pesticide expert.

At the age of 40 he was offered a post dealing with biological warfare at Porton Down, Britain’s chemical and biological laboratory in Wiltshire. It is impossible to exaggerate Dr Kelly’s importance throughout the long campaign to disarm Saddam of his bio-weapons arsenal.

In 1988, while Dr Kelly was working at Porton Down, Iraq tried unsuccessfully to obtain a weapons-grade strain of anthrax from the laboratory. At about the same time, Saddam did manage to get some anthrax from the United States.

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