Five years ago, the tough Glaswegian was earning his living working in a hospital in Saudi Arabia as an anaesthetic technician, putt-ing in canulas, checking doses and weighing patients before they had operations. He and his Thai wife had just had a baby. He was happy and prosperous. Then, on December 17 2000, he was kidnapped by Saudi Arabian police as he got out of his car to walk into the hospital. Handcuffed and thrown into a police van, he was taken to an interrogation room in a prison in Riyadh. At that point, his nightmare began in earnest.

"Two men came into the room," he remembers. "They were Captain Ibrahim al-Dali, who introduced himself as an officer from Saudi Arabian intelligence, and Lieutenant Khalid al-Sabah, the interpreter. Ibrahim was short - hardly over 5ft 5in - but very strong. Khalid was tall and had rotting teeth. They told me I had to confess or they would do things to me that would make me go mad.

"I was totally confused. I had no idea of what I was supposed to confess to. I tried to ask them. Their response was to start hitting me with a pick-axe handle. They beat me all over my body. They brought in a huge 22 stone Saudi to sit on me while they beat the soles of my feet. They forced a metal rod between my knees and hoisted me upside-down, and beat me on my exposed buttocks. It was excruciating."

Mr Mitchell's two torturers eventually told him they wanted him to confess to planting a bomb that had killed another Briton named Christopher Rodway. "They said my wife and son were involved too. It sounded like a joke: my son was a year old." The two interrogators were in deadly earnest. "They kept on hitting me. The only time they broke off was when they went to pray."

That night, covered in blood and bruises, Mr Mitchell was chained standing up to a steel door in a room 5ft by 8ft. Bright lights burnt in his face throughout the night. The moment he looked as though he had fallen asleep, a guard came in and prodded him or hit with a stick to wake him up. And next day, Ibrahim and Khalid were there again, ready with their pickaxe handles.

After three days of torture, Ibrahim and Khalid summoned a doctor to examine Mr Mitchell. The doctor took his blood pressure. It was dangerously high. "Try to relax more," the doctor suggested helpfully to Mr Mitchell. When Mr Mitchell protested that he was being tortured, the doctor calmly replied: "They all say that. You'll just have to cope the best you can." And the moment the doctor left, the torture began again.

Ibrahim then told him that they were going to arrest his wife and son. "We will torture them. When you hear their screams, you will know that they are suffering because you haven't told us the truth."

That threat was enough to break Mr Mitchell. "I was starting to hallucinate because of the sleep deprivation. But I knew I couldn't let them harm my wife and child. I would have done anything to avoid that. I was very frightened for my son and for my wife. Ibrahim said that because she wasn't British, it was even easier for them to make her disappear."

Mr Mitchell's torturers wanted him to sign a confession which implicated Simon MacDonald, an official in the British embassy (he is now the British ambassador in Israel). "They had his picture," Mr Mitchell remembers. "They wanted me to say he had ordered the bombing and that I was working for MI6. It was all absolutely crazy. I invented some names of people I said had ordered me to do the bombing. They discovered the names were invented the next day and beat me extra hard as a result."

Mr Mitchell signed a preposterous confession in which he claimed to have detonated the bomb that killed Christopher Rodway while he was driving his car. "That was easily disprovable. I had receipts which proved that my car was being repaired when I was supposed to have detonated the bomb. The Saudis knew we were innocent from the start," he insists. "I had friends in the police force who told me that they knew the bomb had been planted by Islamic extremists, probably al-Qaeda."

Dr Bill Sampson, another Briton, was arrested on the same day as Mr Mitchell. Raf Schyvens, a Belgian nurse who knew Mr Mitchell, had been arrested and tortured several days earlier. Mr Schyvens had named Mr Mitchell and Dr Sampson as co-conspirators in his nonexistent bomb plot. "I don't blame Raf for that," says Mr Mitchell. "Everyone has their breaking point." Why the Saudi Arabians wanted to frame Mr Mitchell and Dr Sampson remains a mystery. Prince Naif, the Saudi Arabian government's intelligence chief, was determined to blame Westerners for the bomb: he simply refused to accept that Islamic militants were responsible. That Mr Mitchell and Dr Sampson were chosen as culprits may have been just bad luck.

"It was odd," says Mr Mitchell, "because I had assisted anaesthetists twice when Prince Naif was being operated on. I had had him prone on the operating table twice. He had even given me a gold watch as a present for my work. But I was tortured because of the orders of that man."

After he made his confession, Mr Mitchell was forced to go on television with Dr Sampson and Les Walker, another Briton, and repeat it. He thought the torture would then stop. It didn't. "They kept coming to beat me. They would do it for no reason at all. 'What do you want me to say?' I would ask them. 'What questions do want me to answer?' They would reply, 'There are no questions! We just want to beat you.' They enjoyed it. These men were savages."

There was one occasion when they made him kneel down and told him they were going to execute him. He felt a sudden blow to his neck, passed out - and awoke a few minutes later, covered in his own excrement. Ibrahim was laughing at him.

After four months of violence, Ibrahim and Khalid noticed a sudden deterioration in Mr Mitchell's condition. "I kept passing out for no apparent reason," he remembers. They sent for a doctor, who examined him and sent him to the hospital. The stress of the beatings and sleep deprivation had given him a potentially lethal heart condition. "They gave me beta-blockers as medication. The beatings stopped after that."

He was then placed in alone in a tiny cell with no windows. He would remain there for 15 months. "I wanted to die. I thought I was going to die anyway: I was convinced that the only way I would get out of that prison was in a coffin." Earlier, he had been taken out for a trial in a building on "Chop-Chop Square", the notorious location of Riyadh's public beheadings. The trial lasted 10 minutes. The chief prosecutor was Ibrahim, the man who had been his chief torturer. The judges asked Mr Mitchell if he had confessed to the bombing. He tried to explain that he had been tortured - they dismissed that, and announced his punishment: crucifixion, then partial beheading, after which his body would be left out to rot in public.

"In solitary confinement, I lost hope. The routine was soul-destroyingly monotonous. I would hear the call to prayer at 5am. A guard would shove bread and lentils in at about 7am. Then - nothing, nothing at all. Just silence. The tedium was all-enveloping. I was still on the beta-blockers for my heart condition. I split each one I was given and saved one of the halves. When I had what I thought would be enough to kill me, I swallowed the lot. But I survived. The only effect they had was to make me feel ill. I then thought, perhaps I'm not meant to die yet. Maybe God has something else in store."

Mr Mitchell was finally released more than two and a half years after he had been arrested. The bomb that blew up an American military base in 2003 seemed to have made it clear even to Prince Naif that al-Qaeda was responsible for the bombings in Saudi Arabia.

"The first I heard of it," Mr Mitchell, now 49, recalls, "was when the Saudi lawyers came in and said I would be released if I signed a letter to the King apologising for the bomb. I refused. We all did. They came back the next day and said I just had to sign a piece of paper thanking the King for his clemency. I signed that - and soon afterwards, I was on a plane home with the -others. It all happened so fast, I hardly had time to take it in."

Mr Mitchell now lives near Sowerby Bridge in Yorkshire, working part-time as an anaesthetic technician, filling in for those in permanent jobs when they are on leave. For now, he says, it is all that he can manage. He still feels nothing but hatred for the men who tortured him - "they will burn in hell for what they did to me" - but, as he writes in his new book, co-written with Mark Hollingsworth and published this week, he's also very bitter about the way he has been treated by the British government. "The fact that I and the other Britons who were picked up and tortured were released had very little to do with any activity from the British government. The Americans got Mike Sedlak [a US citizen also arrested for the bombing] released within two months. We had to wait nearly three years. Why? Simply because our government is terrified of upsetting the Saudis. They'd rather help British businessmen sign arms deals with the Saudis than stop British people being tortured by them."

What irks him most is that the Foreign Office still hasn't made a public statement in which they proclaim Mr Mitchell and the other men's total innocence and criticise the Saudi Arabians for framing and torturing them. "They won't do it," he says. "The Saudi version of what happened is blatantly ridiculous. Yet the Foreign Office won't contradict it."

Even worse, the British government is supporting the Saudi Arabian government in its appeal to the Law Lords to overturn the decision by three judges on the Court of Appeal to allow Mr Mitchell and the other tortured Britons to sue the Saudi Arabians for compensation. "Jack Straw says that it would be a violation of state sovereignty. He says that the principle that states can't be sued in national courts is one that it is in the interest of Britain to protect - so sorry, we're supporting the Saudis on this one. It's disgusting."

Gov. George W. Bush of Texas said today that if he was president, he would bring down gasoline prices through sheer force of personality, by creating enough political good will with oil-producing nations that they would increase their supply of crude.

''I would work with our friends in OPEC to convince them to open up the spigot, to increase the supply,'' Mr. Bush, the presumptive Republican candidate for president, told reporters here today. ''Use the capital that my administration will earn, with the Kuwaitis or the Saudis, and convince them to open up the spigot.''

Implicit in his comments was a criticism of the Clinton administration as failing to take advantage of the good will that the United States built with Kuwait and Saudi Arabia during the Persian Gulf war in 1991. Also implicit was that as the son of the president who built the coalition that drove the Iraqis out of Kuwait, Mr. Bush would be able to establish ties on a personal level that would persuade oil-producing nations that they owed the United States something in return.

''Ours is a nation that helped Kuwait and the Saudis, and you'd think we'd have the capital necessary to convince them to increase the crude supplies,'' he said.

Asked why the Clinton administration had not been able to use the power of personal persuasion, Mr. Bush said: ''The fundamental question is, 'Will I be a successful president when it comes to foreign policy?' ''

He went on to suggest, as he did in answer to other questions, that voters should simply trust him.

''I will be,'' he said in answer to his own question about whether he would be a successful president. ''But until I'm the president, it's going to be hard for me to verify that I think I'll be more effective.''