Clive Stafford Smith, director of human rights organisation Reprieve, has said he believes Shaker Aamer is being detained in Guantanamo because of what he has witnessed there, not because of his threat to US security.
Mr Stafford Smith, the lawyer representing former Guantanamo detainee Binyam Mohammed, also revealed Mr Aamer broke-down when he saw a photo his youngest son - who he has never met - for the first time.
He said: “I have known Shaker for sometime, because he is so eloquent and outspoken about the injustices of Guantanamo he is very definitely viewed as a threat by the US.
“Not in the sense of being an extremist but in the sense of being someone who can rather eloquently criticise the nightmare that happened there.”
He added allegations Mr Aamer was being gagged were strengthened by an article claiming US government officials may have conspired to conceal evidence three Guantanamo detainees could have been murdered during interrogation.
Harper’s Magazine said three deaths, which were presented as suicides by hanging, could have been suffocations in a secret part of the compound known by guards as “Camp No”.
It also suggested it may explain why the US is reluctant to release Mr Aamer, who has claimed he was part-suffocated while being tortured the same evening.
Mr Stafford Smith, who has visited Mr Aamer in the Cuba prison, said: “They suggests the reason the US has not released Shaker it nothing to do with anything he has done rather it is because the US is afraid of what he was going to say.
“This [article] is merely confirmation, fairly stark confirmation that the reason they wanted not to send him home to his family in England, but rather to send him to Saudi Arabia [his native country] was simply to gag him.”
With numerous claims of torture during nearly eight and a half years of detention [eight of those in Guantanamo with significant periods in solitary confinement] Mr Aamer’s failing health was a concern, Mr Stafford Smith said.
“He has been very damaged by what he has been through. He is a very eloquent person and became the spokesperson for many prisoners in Guantanamo because he has very good English,” he said.
“But I think he has come to a position, there is a position where when you kick a dog, if you keep on kicking the dog, the dog is actually better off than when you are nice to it and I think in a sense that was actually where he was at.”
He said Mr Aamer was respected in Guantanamo “because he has refused to die down to the nightmarish pressures”, but that despite being mentally strong Mr Aamer broke down when shown a family photo, he said.
“The only time I have seen him emotional was over his family. I was able to get pics of the youngest kid into him but that was very heartbreaking for him in a way he didn't want to see it,” he said.
“I saw him for the first time in May 2005 and got a photo into him shortly after that, he really broke down at that because it was so difficult.”
Former Guantanamo detainee Mozzam Begg has said Mr Aamer’s long periods of solitary confinement in Guantanamo Bay were due to him trying to help other inmates, and said his continued imprisonment was nothing to do with a security threat.
He said: “The reason they have Shaker is because of how much he knows. Shaker is an inspirational figure. His personality is such that he was able to talk to the inmates and be a voice for them with the authorities.
“One of the things Binyam [Mohammed] told me is he believes Shaker will not be returned because of a delegation about the hunger strike.
“They tried to break the hunger strike through negotiation but when the Americans renaiged on a deal the hunger strikes restarted and they held Shaker responsible.”
Mr Begg said the Harper’ allegations Magazine added to his belief.
“I always knew there was somewhere secret place outside the perimeter of where the normal military run," he said.
“What surprised me were the allegations of waterboarding, I didn't know about that. It hasn't surprised me the depth of the allegations.”
The source for the article were former Guantanamo guards, one a sergeant.
Mr Begg said: “The only way the authorities can rubbish this [story] now is to rubbish every single one of these soldiers which is going to be ridiculous.
“I'm getting in contact with Guantanamo guards to ask them how this happened. They have got to be brave and step forward and say what took place.”