While five of the British captives in Guantanamo Bay were last night preparing to be reunited with their families, there was no such joy for Moazzam Begg.
The 35-year-old language teacher and law student has been held since February 2002, when he was arrested in Islamabad on the night his wife told him she was pregnant with their fourth child.
Pakistani security forces handed him over to the United States military, who held him for a year at Bagram airbase in Afghanistan, before moving him to Guantanamo Bay, where he is classed as a high-risk prisoner
His family is convinced he is the victim of mistaken identity.
Mr Begg's father Azmat, of Birmingham, last night said he was mystified why his son was not being released with the other Britons.
He said he was "desperately worried" for the health of his son, who he fears has been physically and psychologically tortured, and was planning to fly to Washington next month to demand his release.
"He should be released because he has nothing against him," he said. "It has been two years but that's the equivalent of twenty years."
The release of the other detainees had given him hope, he said, but the family had found it almost impossible to bear the last six months when they have heard nothing from Moazzam.
Azmat Begg, a retired bank manager, first learned Moazzam was being held when his son phoned him to say: "I've been arrested, I'm being taken, I don't know where or why."
His son had been living in Afghanistan for about a year at the time of his arrest, after moving there from Pakistan with his wife Sally and their children.
His family says he was there doing humanitarian charity work, which had been his main interest since he went to stay with relatives in Pakistan when he was 12.
He was helping to set up a school and install water pumps under the Taliban regime in Afghanistan when the US invasion followed the 11 September attacks. Moazzam was arrested, and his savings of about £8,000 were seized, leaving his wife and children to fend for themselves, says his family.
An educated and literary man, Moazzam Begg sold religious and historical books before moving to Afghanistan. Since being held in Camp Delta, he has been sending neatly hand-written letters to his family on paper supplied by the Red Cross.
He has complained of boredom, of coping with sharing his room with 10-legged spiders and of his uncertainty about his fate if it is decided by a secret military tribunal.
His family has been encouraged by evidence that he has retained a sense of humour. In one letter, he said he had read more than 40 books including studies of American history and had been pondering the United States' contribution to civilisation.
After debating the relative merits of the US, ancient Greece, Egypt and China for many hours, he said he had come up with the answer. "Peanut butter - both smooth and crunchy. My co-debater was not amused with the results of my hours of research," he wrote.
In another, he joked about the horrors of the 10-legged camel spider, saying it grew bigger than a human hand and had a bite that made flesh decay.
But in a third, the strains of his captivity were showing. He said he was occupying his time through exercise, conversation, prayer and sleep and in some ways things were getting easier.
However, he told his father: "I... am trying as patiently as possibly to overcome despair."
The last letter the family received last August was what Azmat Begg called a deep and barely comprehensible poem in which his son sounded seriously depressed.
Mr Begg has become one of the main spokespeople for the families of the detainees, helping to lobby the Foreign Office, Washington and European Union and form links with pressure groups such as Fair Trials Abroad and Amnesty International.
He has repeatedly warned his son would not get a fair trial under American military law, and as 200 MPs signed a Commons motion calling for the British suspects to be returned, he urged Tony Blair to use his so-called special relationship with the US to get some action.
He has chosen his words carefully, avoiding criticism of Mr Blair or the Government's efforts, and saying that if his son has done anything wrong he deserves to be punished.
Mr Begg insists that Moazzam has the right to have his guilt or innocence tested by the British judicial system, which he praises as the best in the world.
However his efforts to meet with Government ministers have met with frustration. Last December, he was due to meet Foreign Office minister Baroness Symons for a progress report on efforts to bring his son to Britain. The meeting was cancelled for the sixth time in two years.
He has also written to the US authorities to ask permission to visit Moazzam at Guantanamo Bay, but was refused.
Mr Begg thought the release of the other prisoners meant the US government had to acknowledge that it had no legal right to hold them in the first place.
"The government should both release and apologise for this," he said.
"I will keep on doing whatever I have to do to get him released - I will not stop."