JAMAL al-Harith told last night how he suffered a brutal attack by US military police because he refused to have a mystery injection.
A squad of five men used batons, fists, feet and knees in an assault that left him with severe bruising.
During the beating the officers barked in automated unison: "Comply, comply, comply. Do not resist. Do not resist."
Jamal told how the men swung into action after he politely refused a jab an orderly was trying to give him because he didn't know what it was and he was fit and healthy.
The squad was from the US military's Extreme Reaction Force, a unit trained to hand out beatings and known to prisoners at Guantanamo as ERF.
Jamal said: "I could hear their feet stomping on the ground as they got closer and closer to my cell. They were given a briefing about me refusing the injection, then I heard them readying themselves outside.
"I was terrified of what they were going to do. I had seen victims of ERF being paraded in front of my cell.
"They had been battered and bruised into submission. It was a horrible sight and a frequent sight."
Jamal, who had been warned by interrogators they would inject him with drugs if he did not answer their questions, cowered in his cell awaiting the inevitable.
When it came the full force of heavily protected men in riot gear, with batons and shields, was used against him.
He said: "They were really gung-ho, hyped up and aggressive. One of them attacked me really hard and left me with a deep red mark from my backbone down to my knee. I thought I was bleeding, but it was just really bad bruising.
"I said to myself, 'You shouldn't have put yourself through that', but said nothing to the ERFs. I didn't want to give them the satisfaction.
"There is principle and I wasn't going to take the injection so if they wanted to beat me up that was down to them. This huge black bruise was there for days after that."
But Jamal's ordeal didn't end there. Half an hour later as he was recovering, a second ERF squad arrived to dish out more punishment.
HE SAID: "They accused me of biting a military policeman. I said nothing. I knew it wouldn't help whatever I said.
"They laid into me again. When they were finished I sat down, picked up the Koran and started reading. Then two guards put me in more chains and said: 'Will you comply?'"
Jamal was taken to the feared isolation units, nicknamed ISOs, where those accused of misbehaving are kept in solitary confinement with just a mat and towel.
A toothbrush, toothpaste and soap, considered "comfort items", were denied. Jamal admits this was the first time he cried, although he did not let the guards see he was upset.
He added: "I sobbed a little, twice. Everything had been taken away from me. All I had was my dignity."
Jamal told of the psychological torture used on those in the isolation unit by guards who were trying to break their resolve.
Bright lights were left on in their cells overnight making it impossible to sleep properly. And the rooms were turned very hot in the day or freezing in the early morning by using fans in the ceiling.
Jamal said: "I'd wake up at 3am shivering like crazy. Just to keep a little bit warm I'd try to sleep under a metal bed to protect me from the cold air that was blowing in.
"I'd kept a towel which I hid from a guard to lie on. It wasn't much, but it made things a bit better."
He was put in the isolation unit twice more. Once when he kept ripping off wrist bands with his name and the number 490 written on and another time after guards set up a group of detainees by pretending some spoons had gone missing. Jamal said: "Non-compliance were the favourite words thrown at us."
Jamal told how he was interrogated on a regular basis by FBI and CIA agents and later MI5.
On 40 occasions he was quizzed in chains, which were bolted to the floor, for up to 12 hours at a time.
Jamal quickly became an expert in their interrogation techniques, often turning questions on his tormentors.
He said: "They'd ask me the same thing over and over again. Sometimes I'd say nothing and they asked me why I wasn't responding.
"I'd say: 'You're boring me, ask me something new and I will reply'." After the Americans failed to glean any information, MI5 officers and British consular officials interviewed him. On eight or nine occasions they tried to make him admit he was involved in terrorism.
Jamal said: "They would say: 'Are you a terrorist?' I'd say 'no, get me out of here'."
Speaking about his British interrogators, Jamal added: "They were a mixed bunch. There was one young nervous guy who looked about 21. I called him Youth Training Scheme MI5.
"He wasn't very professional and hadn't even checked out my background. One of them did say they had run my name and details through every Interpol check, but could find nothing. I told them that's because I'm innocent. There's nothing on me. I haven't even got a parking ticket.
"The young guy got a bit frustrated with me and said: 'Are you trying to tell me how to do my job?'
"One MI5 guy I just didn't want to talk to. He kept asking me questions and I'd say 'it's in my file'.
"In the end I said: 'I'm not talking any more.' He replied: 'I've come all this way from England to see you.' I only saw him for 10 minutes. He was very red faced and angry."
Jamal said his US interrogators were much meaner in their approach to questioning.
One told him after not getting the answers he wanted: "We are going to inject you with drugs."
Jamal said: "They were trying everything they could to frighten me. They even staged a mock beating up in the next room to me. They started shouting and pulling a chair around, but I knew there wasn't anyone there because I couldn't hear any chains clanking on the floor."
Another officer threatened Jamal with torture to get a confession. He told him: "Then we will kill your family and you."
Jamal said: "Sometimes they'd joke about what they were going to do to me. But I was determined to show no weakness. I didn't want to let them think they were getting to me.
"Other times they'd play a good cop, bad cop routine. I tried to remain calm, although I was fuming inside. It would been giving in to have lost my temper and I never did, not once.
"I don't swear and I didn't fight back. It was only on principles that I stood my ground.
"The mental torture was far tougher than any of the physical punishments. I knew I was being treated a lot worse than any of the other detainees. They tried everything to break me.
"Ridiculously, they even accused me of being an MI5 spy.
"I began to tease them a little because it was my way of coping. They could never work out when I was serious or not.
I HAD three plaits in my beard. I suggested, although I didn't say it, that it was for three people I had killed during drug deals in Moss Side, Manchester.
"I was making the whole thing up but they believed me. Next time I saw an officer he said MI5 had confirmed the story.
"They couldn't get a handle on me and that frustrated them. In the end one said: 'Who are you?' And I said: 'I've been here for over one a half years and you're asking who I am?'
"I took a stand against them because what they were doing to me was barbaric. I wouldn't get down on my knees for the chains to be pulled around my body because it was demeaning.
"About 20 per cent of us wouldn't co-operate. Eventually they backed down and we would stand while the guards went on their knees to chain us up.
"That was a small victory. There weren't many, but they were memorable. I will cherish them."
Despite the horror, Jamal said there were lighter moments.
One particular interrogation technique amused him. He said: "They started playing different music to see how I would react.
"They started with country singer Kris Kristofferson which I said I quite liked. Then some Fleetwood Mac songs.
"They watched my reactions on camera. I just said the music's great and even started singing along. They didn't play it again."
In the isolation unit, Jamal met for the first time fellow British detainee Tarek Dergoul.
He said: "He was suave and had a pencil moustache. We had a good chat about life back in Britain."
Jamal was released on Tuesday after being flown from Cuba to RAF Northolt, West London.
He arrived back with four other former Guantanamo Bay Britons - Asif Iqbal and Ruhal Ahmed, both 22, and 26-year-olds Shafiq Rasul and Tarek.
They were freed on Wednesday night after being quizzed by anti-terrorist police in London.
Four other British suspects are still being held in Cuba.
Foreign Secretary Jack Straw last night said the US was right to keep the men locked up and the release of the five did not necessarily prove their innocence.
He added: "The Americans as far as they were concerned had good reason for detaining them."
Asked whether they were innocent, he replied: "I can't answer that question, nobody can."