Mr Shubeilat - a bespectacled, bearded engineer, former member of the Jordanian parliament and self-declared Islamist - had been saying the king should obey the constitution, and that peace with Israel should be made not out of weakness but only when Israel "abandons Zionism". And all the while, the military prosecutor's men had hung around us, trying to understand Mr Shubeilat's almost flawless English.
"What did he say to you?" the military prosecutor, Major Mahmoud Oubeidat, wanted to know. Sporting a black moustache, the 39-year-old prosecutor was troubled. "Did Mr Shubeilat criticise his prison conditions?" the major wanted to know. "Did he criticise the State Security Court? What did he talk about?" Islam, I replied, which - up to a point - was true.
Officially, Mr Shubeilat's sins were contained in two speeches he made last November and December, in which he questioned Jordan's peace with Israel and criticised Queen Noor for publicly weeping at the funeral of Yitzhak Rabin, the assassinated Israeli prime minister, while failing to express grief at the assassination by Israeli agents of the militant Palestinian Islamic Jihad leader Fathi Shkaki.
"Tears overflowed from the Queen when she personally attended the official condolence ceremony of Rabin... who had expelled the wife of the martyr (sic) Shkaki from Jerusalem a few months earlier," Mr Shubeilat said. "Yet she (Shkaki's wife) was unable to find a helping hand to wipe her children's brows."
For the King, this was too much. Shubeilat was arrested on 9 December and imprisoned with 1,600 other inmates - accused murderers, thieves and debtors - at Joueida jail, from which he now regularly emerges to appear before the military court. Arab academics and journalists have expressed support for him - the celebrated Egyptian journalist Mohamed Heikal and the Palestinian writer Edward Said have written to his family and Amnesty International has called him a possible prisoner of conscience.
Sitting in the court last week, however, Shubeilat, who at 53 has been re-elected head of the engineering union while still in prison, seemed far from cowed. "I represent the people," he said. "Every person in Jordan knows what I say is right. I support this regime but it must be a constitutional monarchy, not an absolute monarchy. We must have real democracy here. In this court, it is not me who is on trial - it is the government."
Shubeilat's real crime appears to be his opposition to the 1994 peace accord between Jordan and Israel, a treaty made, in his view, out of weakness rather than strength.
"When Crown Prince Hassan (King Hussein's brother) called the unions together two months before the treaty, he looked at me and said: 'Shubeilat, give me your opinion.' I said: 'Look, if you want to have peace because we are weak, then say so and we will oppose you - but we will not be enemies. But if you start selling us peace because Zionism is not racist, then of course we are going to have a clash with you.'
"Do you understand why I said this? I don't say 'no' to King Hussein if he says we must accept defeat - but I do say 'no' when he tells me that this defeat is the dream of our fathers and our grandfathers."
The King, needless to say, claims that peace rather than defeat was the dream of his forefathers. But it remains a fact - despite the support of a parliament whose Islamist opposition was deliberately weakened by changes in electoral laws - that Jordanians are not happy with their new peace and that an ever larger number of the comparatively wealthy middle classes have grown suspicious of a treaty which appears to favour Israel rather than Jordan. If Mr Shubeilat's own opposition is Islamist and - in the view of the government - mischievous, it may nevertheless represent a real and growing sentiment among Jordanians.
"This is why I am in court," Mr Shubeilat says. "Jordanians did not like to see our Queen crying publicly for Rabin on CNN. My reaction was the reaction of every Jordanian. This is enough, I said, this is insulting."
In 1992, Shubeilat was convicted of forming an illegal Islamist group and importing weapons, given a death sentence then mysteriously released only days later under a royal amnesty. The chief prosecution witness, Ali Shekarji, later retracted all his evidence, stating in a signed affidavit that he had been blackmailed into concocting his evidence against Mr Shubeilat by named officers in the Jordanian intelligence service.
There can be no doubt that he is a thorn in the King's side - which may be why Hussein once offered to make him a royal adviser, an offer he turned down, according to his wife, Rima, because he insisted on two conditions: that he and his fellow advisers would be unpaid and would not be offered any future posts in the government.
After criticising the government's policy towards Iraq - because the King called for democracy in Baghdad but not in Riyadh or Bahrain - Shubeilat says he was summoned to the Royal Court.
"The King personally warned me," he says. "He said 'do you want what happened to you before to happen to you again? Because this time I won't interfere.' But what can I say? I must be free to speak. If they keep me in prison, it will become a nightmare for the government. If they assassinate me, my blood and soul will topple the King." Was he really suggesting that he might be murdered? Jordan, I said, was not Iraq and nobody in the West was going to believe differently.
"I'm not seeking it [death]. But I'm not escaping it. I have a destiny I have to meet." This seemed a little melodramatic, I said. Was life that bad? "I'm having a ball in prison - I had my best Eid feast ever [at the end of Ramadan]. I know what I'm doing. I am happy." The court resumes this week.