The anaesthetic technician initially thought he had been kidnapped. After an hour and several beatings the hood was taken off and he found himself in the Mabatha Interrogation Centre. His abductors were, in fact, Saudi secret policemen.
More than a decade later, Mitchell relives his ordeal almost matter-of-factly. But the nightmare in which he found himself is still difficult to comprehend.
"The beatings just carried on straight away because they were in a rush to break me as quickly as possible.
"It was a total of seven days and nights of sleep deprivation. I was chained up to the door when my interrogators were resting so I couldn't sleep," he said.
"The beatings were frequent and they beat me until I became unconscious, then water would be poured over me to revive me and the beatings would start again.
"They would always use axe handles, like they didn't want to get their hands dirty.
"Between torture sessions they would stop at prayer times and go and wash and pray and come back and carry on the torture as if nothing had happened."
Mitchell was accused of being involved in a bombing campaign which began in November 2000 when an explosion killed British engineer Christopher Rodway as he was driving his car.
The Saudi authorities alleged the bombings were related to a feud between rival ex-pat groups controlling trade in illicit alcohol. The men all maintained their innocence and counter-claims were made that Islamist terrorists were behind the attacks.
Following a forced confession, broadcast on Saudi television, Mitchell was sentenced to a brutal public execution which involved being tied to a wooden cross and partially beheaded.
The British men were given a royal pardon and released in August 2003, with Saudi officials denying they had been tortured. Five Saudis were transferred from the US prison at Guantanamo Bay in exchange for their release.
An inquest into Rodway's death in 2005 concluded there was nothing linking Mitchell to the fatal explosion.
Mitchell said he was "very disturbed" mentally and found it difficult to even put sentences together when he came back from Saudi.
But he has tried to put his ordeal behind him for the sake of his family - wife Noi, 15-year-old son Matthew and eight-year-old daughter, Tara.
"It is always in my mind. I don't get flashbacks as frequently as I used to, but I still get nightmares and it still haunts me.
"If I'd been taken prisoner by al-Qaeda or the Taliban I could perhaps understand it, but Saudi Arabia was supposed to be an ally of ours.
"My friend, Dr William Sampson, who died last year, was raped by his interrogators. He spent his last years waiting and hoping for justice that never came.
"I have a responsibility to provide for my family and I feel I have got a responsibility to continue our campaign to highlight the injustice and the corruption that has gone on."