Few of us really understand the reality of the US torture outlined in this week’s Senate report. Among those who do is the Londoner, Guantánamo prisoner and Reprieve client Shaker Aamer. I saw him this week. Unlike the assorted people who offer themselves as experts to comment on CIA torture, Shaker is a true (if involuntary) expert in the field. Yet he is unable to share his views.

The first problem, of course, is that I could not show him the report. The US may spend $2.7m for each prisoner, each year, on housing people beyond the rule of law, but Wi-Fi in Guantánamo does not work very well; and, even if it had done, the censors would not have let Shaker read it. Had it got to him, Shaker might have expressed strong views, but anything he said would have been censored with equal vigour.

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Instead, then, let me posit what Shaker would say if he were free, or even merely free to speak.

Shaker might describe his own terrible ordeal. He might express surprise that he is not named as a victim in the hundreds of pages. He might, indeed, wonder how it could be that so few of the 779 Guantánamo victims of torture are mentioned.

He might wish to issue a parallel report of his own describing how, in late 2001, he was sold to America by a bounty-seeking Afghan warlord and transferred to US custody at Bagram air force base. He might tell you how he was kept awake for over a week, chained in excruciating positions for hours, deprived of sleep and food, and doused in freezing water at the height of the Afghan winter.

He might describe the impact of having his head slammed against a wall – in the presence of a British agent. He might wonder why Britain did nothing then, all those years ago.

He might query why the single most important catastrophe of the torture programme receives so little attention. Shaker was Prisoner 005 in Bagram, and he witnessed Ibn al-Sheikh al-Libi being taken out in a coffin. The CIA erroneously thought that Libi, who was actually at odds with Osama bin Laden, was number three in al-Qaida. They flew him to Egypt where he was subjected to torture by electric cattle prod. Once there, he “confessed” that al-Qaida and Saddam Hussein were in league together, trafficking in weapons of mass destruction – a false and bitter fruit of torture that was wheeled out to justify the invasion of Iraq, and only discredited after many thousands had died.

Shaker might wonder out loud why Britain went along with President Bush’s deadly charade.

Shaker might go further and explain that, notwithstanding President Obama’s protestations, the torture yet continues. In Guantánamo, he is still confined to a 6ft by 8ft windowless cell, forced into solitary confinement – his punishment for being “noncompliant”. He’s been a regular victim of brutal force-feedings, and he has been beaten by the “forcible cell extraction” team more than 300 times.

Shaker might remind us that he is a British resident with a British wife and four British children waiting for him in London. He would doubtless explain that he has been cleared for release for seven years through a process that requires agreement by six different US agencies to agree that he is no threat to anyone.

Most who read the CIA report express horror that the US could have diverged so far from the path of civilisation. In truth, Shaker does not really need to see it; he lives it, every day. What he does need to know, though, is why Britain – the closest ally to the United States – cannot rescue him.