His release from captivity was only finally authorised by US authorities on February 20 and announced by the British Foreign Office. This was despite the US dropping all charges against him in October of last year. In December he was "unofficially" told that he was to be released when the Obama administration assumed office in January.

His freedom comes after years of systematic torture and abuse, and no evidence linking him to terrorist activity.

Upon his arrival, Mohamed released a statement re-iterating allegations that he was tortured by US agents in Pakistan, Morocco and Afghanistan between 2002 and 2004, and that Britain's security agencies were complicit.

Pleading for time to recover from his seven-year ordeal, Mohamed wrote, "I hope you will understand that after everything I have been through I am neither physically nor mentally capable of facing the media on the moment of my arrival back to Britain."

He continued, "I have been through an experience that I never thought to encounter in my darkest nightmares. Before this ordeal, ‘torture' was an abstract word to me. I could never have imagined that I would be its victim. It is still difficult for me to believe that I was abducted, hauled from one country to the next, and tortured in medieval ways—all orchestrated by the United States government".

Of those remaining in captivity he said, "While I want to recover, and put it all as far in my past as I can, I also know I have an obligation to the people who still remain in those torture chambers. My own despair was greatest when I thought that everyone had abandoned me. I have a duty to make sure that nobody else is forgotten."

Mohamed wrote that hundreds of people are still held without charge in Guantánamo Bay, and that "there are thousands of other prisoners held by the US elsewhere around the world, with no charges, and without access to their families."

He added, "For myself, the very worst moment came when I realised in Morocco that the people who were torturing me were receiving questions and materials from British intelligence. I had met with British intelligence in Pakistan. I had been open with them. Yet the very people who I had hoped would come to my rescue, I later realised, had allied themselves with my abusers.

"I am not asking for vengeance; only that the truth should be made known, so that nobody in the future should have to endure what I have endured."

The government of Prime Minister Gordon Brown has authorised a limited investigation, led by the Attorney General Baron Williams of Mostyn, with its remit limited to whether or not there should be a further criminal investigation. But Mohamed's allegations have prompted senior political and legal figures to call for a full judicial inquiry.

Conservative Party MP David Davis, who has sought to project himself as a champion of democratic rights, said in an interview with the BBC, "I am convinced...that Binyam Mohamed was actually tortured." He added, "I am pretty convinced that we knew about it, and I'm reasonably convinced—I think there's a prima facie case—that we colluded in it in some way."

Davis said that if Mohamed's statements proved to be true, then "a huge number of laws had been broken," and attempts to cover this up would also mean the government had broken the law.

In an interview with the Sunday Times, Lord Carlile of the Liberal Democrats said that a judicial inquiry was needed and also called for an inquiry into the treatment of Iraqi "terror" suspects whom the British government has admitted were handed over to the US by the SAS in 2004 and then rendered to Afghanistan. The two men, known to be Pakistanis, were seized by the SAS outside the UK-controlled zone covering south-eastern Iraq.

The government has refused to accept any calls to hold a judicial inquiry, with Deputy Prime Minister Harriet Harman saying, "At the moment we have got an investigation by the attorney general."

The intervention of Lord Carlile is not without significance and underlies the unease in ruling circles, who fear its political ramifications. He is the independent adviser charged by the home secretary with reviewing implementation of the government's terrorism laws.

He demanded that "an independent inquiry should be appointed to be conducted by a senior judge or a retired judge or someone similar" into the case of the Iraqi detainees and Binyam Mohamed. He said the inquiry would have to investigate allegations of UK complicity "in the rendition of captured men and women to foreign governments." But, aware of its politically explosive nature, he called for any such inquiry to be heard in private.

Commenting on the possible scope of such an inquiry, the Times wrote, "A criminal investigation would raise the prospect of an MI5 officer being charged with torture or war crimes and facing an Old Bailey trial.

"The MI5 case files could also throw light on the role of Jonathan Evans, the director-general of MI5. At the time of Mohamed's alleged mistreatment, Evans was the MI5 director responsible for counter-terrorism.

"Since Mohamed was suspected of plotting a dirty bomb attack in the US he was considered a ‘priority' suspect for MI5. Evans would almost certainly have been aware of his interrogation, and he is likely to be interviewed by detectives if there is a police inquiry."

The Times also reported that UK government ministers were informed about the fate of the two people in Iraq that the SAS handed over to US forces. It stated, "Jack Straw, then foreign secretary and Charles Clarke, then home secretary, were told about the two cases in briefing papers given to them by officials in April 2006. Hutton claimed Straw had not spotted the significance of the cases because it had not been highlighted by his officials."

The web of lies, disinformation and deceit woven by the governments of Tony Blair and Gordon Brown surrounding the Iraq and Afghan wars, and the "war on terror" more generally, is unravelling.

Last week the defence secretary, John Hutton, admitted that ministers had misled parliament about the role of the UK in rendition in the case of the two Pakistani men. Hutton said that the two Pakistanis were still being held in Afghanistan.

British government involvement in their capture and "rendering" first came to light last year when Ben Griffin, a former SAS soldier, alleged that British troops had handed them over to the US. In his statement Griffin alleged that Iraqis and Afghans were captured by British and American special forces, before being rendered to prisons where they faced torture. Following these revelations, the UK Ministry of Defence was able to obtain a court order preventing Griffin from making public further details on the matter. The gagging order remains in force.

Hutton's admission is the first such occasion when the British government has acknowledged the role of UK security forces in handing over the prisoners to the US. Whilst admitting UK complicity, he claimed that the two were transported to Afghanistan because of a "lack of relevant linguists necessary to interrogate them effectively in Iraq."

Last year the government was also forced to admit that US aircraft transporting abducted prisoners landed on the British dependent territory of Diego Garcia in the Indian Ocean in 2002. This too had been previously denied.

A statement released by the human rights group Reprieve said "that the UK has colluded with the US in the illegal practice of extraordinary rendition." Executive Director Clare Algar commented, "This government has misled us again and again. First, they said that Diego Garcia was not used for rendition flights; then they had to admit that they had misled us on that.

"Then they said that the security services condemn torture, yet it seems that those services were complicit in the torture of Binyam Mohamed. Now the defence secretary tells us that, despite previous assurances to the contrary, British forces handed prisoners to US forces in Iraq whom the US have rendered to Afghanistan. Surely we must immediately have the public inquiry into the government's conduct of the ‘War on Terror' demanded by so many."