Alexander Litvinenko claimed in a 2001 book, banned in his native Russia, that the Kremlin's security service had created a secret unit to hunt and kill those considered a danger to the state.
Alexander Litvinenko claimed in a 2001 book that the Kremlin's security service had created a secret unit to hunt and kill those considered a danger to the state at home or abroad.
As he lay critically ill under armed police guard in a London hospital yesterday, after apparently being poisoned, the former KGB lieutenant-colonel's allegations seemed grimly prophetic. In an assassination attempt as laden with high politics and low treachery as a Cold War thriller, Mr Litvinenko fell ill on the sixth anniversary of his arrival in Britain, after meeting an Italian KGB expert in a sushi bar near Piccadilly Circus.
He was given a 50-50 chance of survival after ingesting thallium, a toxic metal known as the "secret agent's poison" because it is lethal in doses as low as one gram and is administered as an odourless and colourless salt.
Sources close to Mr Litvinenko said he believed the Russian Federal Security Bureau (FSB), the successor to the KGB, poisoned him to stop four agents being named as suspects in the murder of the journalist Anna Politkovskaya who investigated human rights abuses in Chechnya.
Mr Litvinenko, 50, said his Italian contact, Mario Scaramella, gave him documents purporting to name the gang responsible for organising the shooting of Ms Politkovskaya outside her Moscow apartment last month. Mr Litvinenko, a thorn in the side of President Vladimir Putin's government since he turned whistleblower on the FSB in 1998, had recently begun looking into her death.
Scotland Yard's serious crime directorate began investigating the " suspected poisoning" on Friday, six days after it became public. No arrests have been made.
In his book, Blowing Up Russia: Terror From Within, Mr Litvinenko claimed the FSB had set up a private security firm called Stelth which contracted crime gangs to carry out killings. In 2003 an order of 4,500 copies of the book for Prima News were seized just outside Moscow by the FSB. The book, funded by the oligarch Boris Berezovsky, also alleges that the FSB was responsible for blowing up apartment blocks in Moscow and blaming it on Chechen rebels.
A friend of Mr Litvinenko said: "Alexander is certain the FSB has tried to murder him because he got too close to the Politkovskaya case. He believes they followed him to the restaurant and administered the poison. He thinks he should already be dead."
Akhmed Zakayev, the London-based Chechen separatist spokesman, said: " This was the FSB. Anyone who dares criticise Mr Putin is at risk."
Sources said Mr Litvinenko, who became a UK citizen last month, needs a bone marrow transplant if a donor can be found. He has not eaten for 18 days because of vomiting and has lost his hair. The thallium, once used in rat poison, has damaged his kidneys and destroyed most of his white blood cells.
Alex Goldfarb, the executive director of the International Foundation for Civil Liberties, who helped smuggle Mr Litvinenko out of Russia in 2000, said: "He looks like a ghost. He's a fit man. He never smoked, he never drank and he would run five miles a day.
"But now he has lost all his hair. He has inflammation in the throat so he cannot swallow he has to be fed intravenously. He can speak only with difficulty. Alexander Litvinenko was one of the most vocal voices [against the FSB]. For them, it's a vendetta for life."
Doctors believe that the former agent, who joined the KGB in 1988 and then worked for the FSB dealing with organised crime groups, is only alive because of his fitness, and because he had been trained to empty his stomach after a suspected poisoning by inducing vomiting.
Mr Litvinenko, who lives with his wife, Marina, 44, and one of his children in a north-west London suburb, met Mr Scaramella at a branch of Itsu at 3pm on 1 November.
In an interview with the Russia news agency Izvestia before his condition deteriorated last week, he said Mr Scaramella called him unexpectedly that day and they agreed "as usual" to dine at the restaurant.
"I ordered the food and he took just water and was hurrying me," Mr Litvinenko said. "From the text of the documents, I understood that the mentioned people could have arranged the murder of Anna Politkovskaya. We parted nearly at once. As soon as I got home, I fell down."
He was admitted to Barnet General Hospital within two days of falling ill but friends claimed that the cause of his sickness was not identified for a further nine days until tests were performed at Guy's Hospital. He was transferred to University College Hospital on 11 November.
How the poison was administered and whether it happened before or after the visit to Itsu is unknown.
Police have visited the restaurant but it is not equipped with CCTV cameras. There is no suggestion that Itsu or its staff were involved in the poisoning.
There is also no evidence that Mr Scaramella had any knowledge of the attack. The Italian, described variously as a magistrate, academic and expert on environmental crime, refused to comment on the case.
But he said that he was concerned he might have been affected by the same poison and was waiting to be tested at a hospital in Rome. "It is a very strange situation."
Mr Scaramella, who was a consultant on the Mitrokhin Commission set up to investigate the activities of the KGB in Italy during the Cold War, was the target of a failed Mafia hit in 2004.
He was also the source of a story which captivated the Italian press last year with a claim that Soviet destroyers laid nuclear torpedoes in the Bay of Naples in 1970.
Much remains to be explained about the attempted poisoning of Mr Litvinenko. Sources who have seen the documents provided by Mr Scaramella suggest they cast little new light on Ms Politkovskaya's death.
Supporters of Mr Litvinenko have spent the past fortnight tracing his movements up to 1 November. He is said to have met another contact on that day, an unnamed Russian journalist who flew to London from Moscow and then returned shortly afterwards.
The Kremlin gave no response to Mr Litvinenko's case yesterday. But few in Mr Putin's administration will spend much time worrying about his well-being.
In official circles, Mr Litvinenko is regarded as a traitor and a fantasist bent on blackening the Kremlin's name. His decision to style himself a supporter of Chechen rebels has won him few friends.
He first came to public prominence in 1998 by claiming at a press conference in Moscow that he had been ordered by his FSB superiors to assassinate Mr Berezovsky, who helped Mr Putin rise to power but had subsequently fallen out of favour. The FSB categorically denied the claim.
Mr Litvinenko fled to the UK in 2000, assisted by aides of Mr Berezovsky, who have also given him financial support. Both men are the subject of active extradition efforts by Russia. They deny any wrongdoing and claim they are the subject of fabricated charges.
During his time in London, Mr Litvinenko has made a number of high-profile claims. As well as the allegations in his book, he has suggested that al-Qai'da's number two, Ayman al-Zawahiri, is a former KGB agent.
In 2003, he tipped off Scotland Yard about what he said was a plot to kill Mr Putin. He claimed that the would-be hitman told him of the plan during a meeting outside a noodle restaurant in Leicester Square.
Detectives arrested two Russian men but let them go a few days later on condition that they return to Moscow.
Echoes of the Markov murder
By Thair Shaikh
The thallium poisoning of Alexander Litvinenko has echoes of the Cold War assassination in London of the Bulgarian dissident Georgi Markov with a ricin-tipped umbrella.
Markov, a BBC Word Service journalist who settled in the UK after defecting to the West, was stabbed in the ankle while waiting at a bus stop on Waterloo Bridge in 1978. An assassin from the Bulgarian secret services used a specially adapted umbrella to push a deadly 1.7mm-wide pellet containing ricin into Markov's skin. Markov said he experienced a sudden stinging pain, but continued his journey. He died three days later in hospital.
Last year the name of the alleged assassin, codenamed Agent Piccadilly, appeared in leaked files. Francesco Guillino, a Dane of Italian origin, allegedly flew to London three times in 1977 and 1978, leaving the day after Markov was hit.
In 1992, General Vladimir Todorov, the former Bulgarian intelligence chief, was jailed for destroying material relating to the assassination. Stoyan Savov, who ordered the murder, killed himself before trial. After the regime collapsed in 1989 a stack of special umbrellas was found in the interior ministry.