The witness said Lee Brown, 39, told him: ‘Please, please help me. Call my embassy, call my family … They beat me badly. Please help me otherwise I will die.’

His testimony includes the claim that after being attacked by six officers, Mr Brown was left alone for four days to die in his cell and that no officers checked on him.

The officers, he says, even joked: ‘He’s crazy. Let him die in there.’

Mr Brown, a handyman from Essex, had flown first class to the Gulf city and was staying at a £1,400-a-night hotel when he was arrested after a row with a maid and jailed.

Reports from inside the notorious Bur Dubai police station claimed that his police guards had beaten him and smashed his head against the concrete floor. But no credible, in-depth testimony has surfaced from anyone who was inside the prison – until now.

The Mail on Sunday tracked down the one inmate who shared a cell with him – making him one of the last people to see and speak to him before his death.

The witness – whose identity cannot be revealed because of fears for his safety – has since been released and is assisting the victim’s family to find the truth. In an interview, he describes being thrown into the same cell after arriving at the police station in the aftermath of the alleged beating.

His evidence reveals how Mr Brown was covered in blood from ‘awful’ head injuries and how the guards had apparently humiliated him by pulling down his jeans so his genitals were visible. Four days after leaving Mr Brown to die, the witness says police removed his body in a black bin bag.

Mr Brown, a man of modest means from Ilford, Essex, set off on what should have been a spectacular holiday in Dubai less than three weeks ago. Flying first-class on Emirates and staying in the seven-star Burj Al Arab, billed as the world’s most luxurious hotel, it is believed he was planning to meet a woman he had befriended on the internet.

But early on Thursday, April 7 – just hours after checking into the hotel – he was arrested after a confrontation with a chambermaid. Officers took him to the Bur Dubai police station – notorious as the most brutal in the city. Other prisoners later told the witness they had seen a gang of six guards laugh as they beat Mr Brown with kicks, punches and batons. They said they smashed his head against the ground and a wall.

It was soon after this alleged attack that the witness was taken to the jail on April 8, after being arrested for a minor offence.

He said: ‘When I got there the officers were immediately aggressive. One shouted: “Go, go, go. Get inside! Stupid boy. I will slap you. I hope you die in here.”‘

He was taken, by accident he believes, to a tiny, windowless cell where Mr Brown had been dumped and was alone with him for a crucial ten minutes before he was moved.

‘The door opened,’ he said. ‘I saw Lee leaning against the far wall of the cell with handcuffs on his wrists and ankles. He was naked apart from his dark green jeans which had been pulled down. It looked like they had done that to humiliate him.

He was half-conscious but he noticed me when I came in.

‘He was in a very bad way and clearly needed emergency treatment. He was bleeding from many wounds on his head and face. It was mainly coming from his right forehead and was running all the way down his chest. The blood was fresh so I would have said he was injured one hour before. There were streaks and pools of blood across the concrete floor.

‘His skin had been ripped off his arms and shoulders and there were large scratches down his chest.

‘The shackles were fastened so tightly they cut into his skin and so his hands and feet were white. And, despite it being at least 86F in there, his body was shaking and his lips and face were blue.’

He recalls how the Briton told him in a low voice: ‘Please, please help me. Call my embassy, call my family.’ Asked what happened, he said: ‘They beat me. They beat me badly. Please help me otherwise I will die.’ After this, the witness says, he closed his eyes and did not respond again.

After ten minutes, the guards moved the witness into the main cockroach-infested room, where 600 prisoners sleep crammed in on ‘disgusting’ mattresses.

Over the next four days, he says he was stunned by the actions of the police officers as they left Mr Brown to rot in his cell, not once checking on him, tending to his injuries or feeding him. The inmates could not see him through the flap as the bed was to one side, but they could see a plate of food on the floor.

The witness said: ‘Through the flap I couldn’t see him, but I could see a plate of disgusting chicken and rice that had been there on Friday. Over all those days, it was never eaten and the plate was never changed.’

The inmates went through Lee’s belongings and found a phone number for his family, which they called on April 11 on a smuggled mobile. His family contacted the Foreign Office early the next day. Later on that morning – at least four days after the alleged beating – the British Embassy contacted Dubai police, to be told that Mr Brown was in a good condition and was declining consular assistance.

According to the witness, at about 8pm that evening six officers finally arrived in the cell.

He said: ‘One was very seniorlooking From the way their faces looked and they talked, they were very scared. They went in and took pictures of the cell. Then we saw them carrying his body out in a black rubbish bag. You could see one of his naked legs sticking out.

‘An hour later they opened the cell again. Once the officers had gone we went in. There was blood on the bed and the floor. And that same food was there untouched.’

The witness also revealed the bizarre hierarchy that was enforced among prisoners in the jail. He said: ‘Locals had a clean area with proper beds, air-conditioning, mineral water, television and could order restaurant-style food such as spaghetti bolognese from the canteen.

‘The other prisoners are woken at 5am to be fed a breakfast of five haricot beans in a horrible salty sauce with tough Arabic bread. It is disgusting, not even food. I would not give it my dog.’

The witness was released from the police station days later.

Last week Mr Brown’s brother Steve and sister-in-law Su flew to Dubai to speak to the authorities and the British Embassy.

Last night Steven said: ‘Lee was dearly loved by his family and friends. He was a caring son and a wonderful brother and his loss will leave a gaping hole in our lives. We will not rest until the truth about Lee’s death comes to light.’

Steven and Su also met the witness featured in this article, who has promised he will testify to a court.

He said: ‘The police made a big mistake with Lee and hopefully they will now have to pay for it.’