Apparently we can know (almost for sure) that he was tortured, but not see the evidence shown to British judges. The Guardian:
The high court yesterday condemned as “deeply disturbing” a refusal by the US government to disclose evidence that could prove a British resident in Guantanamo Bay was tortured before confessing to terrorist offences.
The court said there was “no rational basis” for the US failure to reveal the contents of documents essential to the defence of Binyam Mohamed, who faces the death penalty.
[...] David Miliband, the foreign secretary, conceded there was an “arguable case” that Mohamed had been subjected to torture and inhuman treatment. Yet Miliband also wanted to suppress relevant documents, not because they would reveal any intelligence operations but because the US claimed that if they were disclosed serious harm would be done to “intelligence sharing” between the UK and the US.
The judges said it was clear Britain had “facilitated” Mohamed’s interrogation when he was unlawfully detained in Pakistan before he was secretly rendered to Morocco, Afghanistan, and then to Guantanamo.
[...] They noted that a military prosecutor at the US base had recently resigned in protest against the treatment of prisoners, including the use of a “frequent flyer programme”. The judges described this as a “euphemism for a sleep deprivation programme”. They added: “This is a practice which the United Kingdom expressly prohibits.”
Charges against Mohamed — including that he was involved in a dirty bomb plot — have been dropped, allegedly to prevent the US from revealing torture evidence. The US authorities now planned to charge him with other offences, the judges noted yesterday.
[...] Mohamed, 30, an Ethiopian national and British resident, was held in Pakistan in 2002, when he was questioned by an MI5 officer. He was later secretly rendered to Morocco, where he says he was tortured by having his penis cut with a razor blade. The US subsequently flew him to Afghanistan and he was transferred to Guantanamo Bay in September 2004.
The Guardian’s profile of Binyam Mohamed, says he was caught while trying to use a false passport.


The Telegraph reports that:
Another Telegraph story says:
Maybe British Intelligence has no faith in its own work?
By: Lister on February 8, 2009
at 8:23 pm