The deposed dictator, once a paunchy figure in military fatigues, has lost almost a stone by exercising in his maximum security detention facility at Baghdad Airport, said General Richard Myers, chairman of the US Joint Chiefs of Staff.

“My understanding is he’s lost about 12lb, on purpose, and he’s worked out twice a day,” General Myers said in a television interview after the court hearing.

Saddam has exhibited a mental as well as physical discipline in prison. He has refused to divulge any important information that could be used against him, officials close to the interrogation said.

One source said that although very little real intelligence has been gleaned from more than six months of interrogation, interviews with the ex-dictator revealed some surprising twists of logic.

Saddam reportedly hinted that his vagueness over whether or not he possessed weapons of mass destruction — an elusiveness that eventually cost him his country and may yet cost his life — was a ploy to “keep the neighbours at bay, while the US would be hung up in interminable debate in the UN”.

The regime appeared to have been taken by surprise when US and British forces unleashed a lightning war. Documents seized after the invasion show that even as hundreds of thousands of troops poured across the border from Kuwait, the self-appointed field marshal believed the main thrust would come from Jordan.

Saddam also told his interrogators that the main reason he invaded Kuwait in 1990 was not, as he claimed in court, to defend Iraq’s honour, but to keep his officer corps too preoccupied with fighting an external enemy to plot coups against him.

Speaking only in Arabic, although he knows rudimentary English, the former President also recalled how he had locked his violent son Uday in solitary confinement for beating to death a man who played his music too loudly. Uday and his brother Qusay were both killed in a shoot-out with American forces in Mosul a year ago.

The interrogators, who used psychological rather than physical pressure, said that Saddam gave away almost nothing about his six months on the run, or his whereabouts when US bombers struck houses he was believed to have been occupying in the early days of last year’s war.

Saddam has seen the inside of a jail before: he was arrested for six months in 1958 on suspicion of murdering a political rival of his uncle’s, and served two years for a plot to assassinate Iraq’s leader in 1964. His second term ended when he escaped from jail.

Saddam used his court appearance to challenge the court’s legitimacy, defend his invasion of Kuwait and insist he was still the rightful President of Iraq.

His outbursts seemed designed to exploit the nationalist sentiments of some Iraqis, particularly Saddam’s fellow Sunni Muslims.

Among Iraq’s polarised population there was both delight and anger at his court appearance yesterday. Around 3,000 Shias staged a rally in Baghdad demanding his execution. At the same time hundreds massed in the Sunni stronghold of Samarra, north of the capital, to support Saddam and denounce his trial.

Across the Arab world opinions were also divided. In Saudi Arabia, Arab News said his defiance was no surprise. “He never, in his long and wicked political career, accepted the rule of law,” it wrote.

In Khartoum the editor of Al-Adwa newspaper wrote: “It is Saddam who is now putting on trial those who imprisoned him.” He “will have the street on his side”.

Some Arab newspapers gave warning that televising the court sessions could give the former leader a platform to reach his people.

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