An all-party parliamentary watchdog is investigating allegations that British intelligence agents were involved in the abduction and torture of 28 Pakistani immigrants in Greece following the 7 July bombings.
One of the immigrants showed documentary makers how he was hooded by his captors
In a BBC Radio 4 documentary, 10 of the Pakistanis tell BBC correspondent Malcolm Brabant how they were threatened, just before being told they were innocent, and then dumped, hooded, back on the streets of Athens.
A careless remark during a conversation about going to the lavatory has given the strongest indication yet that British intelligence agents might have been involved in the seizure of 28 Pakistanis in Greece.
The Pakistanis have alleged that they were kidnapped and psychologically tortured in a joint Greek-British operation which took place a week after the London bombings of 7 July last year. The British Foreign Office has denied British involvement.
One of the 28, whom the BBC is calling "Mr R" after he asked to remain anonymous, told me about an encounter with an English-speaking agent on day two of his interrogation.
"All the conversations with me took place in the Greek language. One time there was one man who was passing by.
"He peeped into our room. I said to him (in Greek) ,'Can I go to the toilet?' and he replied (in English) 'I don't know Greek.'
"'His skin colour was pinkish like white people, not particularly fair skinned, but white."
Several of the 28 have described seeing a black officer present at the interrogations who also spoke English to them.
Jack Straw described the allegations as "nonsense"
"I would have to assume the black officer was either from MI6 or Scotland Yard," said Brady Kiesling, a former political officer at the American Embassy in Athens, who has now retired from the US state department after 20 years of service.
"I have never seen a black Greek police officer."
British Foreign Secretary Jack Straw declined to be interviewed for the programme "Spies and Lies: An Athenian Mystery", or to waver from his original declaration last December, that the allegations that British personnel were involved in the abduction and abuse of the Pakistanis in Greece were "complete nonsense".
Britain's all-party Intelligence and Security Committee is currently investigating the allegations and is due to report in the summer.
Its chairman, Paul Murphy MP, says he has no reason to doubt that Mr Straw is telling the truth.
Despite Mr Straw's denial, it seems clear that the questioning of the Pakistanis was specifically designed to assist the British inquiry into the London bombings.
The reason the 28 were targeted was because their phone numbers appeared in an electronic trail that British detectives were keen to pursue.
Greek Public Order Minister George Voulgarakis told MPs that after the London bombings, the British authorities asked the Greeks to investigate suspicious phone calls made by people they suspected of being al-Qaeda sympathisers.
The minister said that during the course of the next two months, the Greeks questioned 5,000 economic migrants. Mr Voulgarakis insisted that the 28 Pakistanis were not among the 5,000 rounded up.
Some of the detainees allege they were beaten. All of those interviewed by the BBC claim they were hooded, which is classified as torture by EU and UN Conventions.
But the most egregious element of their complaint is that they were held incommunicado for up to seven days, without access to a lawyer, as required by Greek law.
"It reminds people of what happened during the [military] dictatorship of 1967 to 1974," says Panos Garganas, an engineer from Athens Polytechnic, a place which came to symbolise Greek democracy after the colonels sent in tanks to crush a student uprising, killing dozens of young protestors.
"You would have friends or relatives disappear, and people would wander around in hospitals and police stations trying to find out what happened and getting no reply."
'We will slit your throats'
The case of the Pakistanis has become a cause celebre in Greece. After a public prosecutor began a formal investigation, the detainees gained confidence to reveal more details of their experiences. For months they had been too frightened to talk.
Gul Nawaz, a young man who claims to have been beaten during his spell in detention, says they were threatened just before they were told they were innocent, hooded again and dumped onto the streets of Athens.
Nawaz says they were told: "If you ever mention this thing to anyone at all, or you say where you were taken to, or you talk to television, radio or newspapers, then we will you catch you and bring you in again and trust me, we will kill you.
"We will slit your throats."
Spies and Lies: An Athenian mystery: BBC Radio 4, Monday, 6 February, 2005 at 2000 GMT.
You can also listen online for 7 days after that at Radio 4's Listen again page.