'THE view inside our agency was that poison is just a weapon, like a pistol." Almost two years ago, when the Ukrainian presidential election campaign was catapulted to the world's attention by the poisoning of Viktor Yushchenko with dioxins, an ever-quotable former Russian spy named Aleksandr V Litvinenko warned that such behaviour was perfectly natural within the new security regime that had grown out of the ruins of the feared KGB.
Moreover, Litvinenko explained, the KGB's successor, the Federal Security Service (FSB), maintained a secret poisons laboratory dedicated to producing deadly chemical weapons for use against enemies of the state. "It's not seen that way in the West, but it was just viewed as an ordinary tool," Litvinenko added.
He was never under any illusions about the furtive nature and destructive power of the organisation he had abandoned. Last Thursday evening, according to his family, friends and - in a chilling testament from his death-bed - Litvinenko himself, he became the latest victim of that clandestine poison factory and the merciless government machine of Vladimir Putin, which has been pursuing him since he walked out on Russia for the West. His laborious battle against the radioactive toxins which had somehow found their way into his body ended in a London hospital and in the full glare of the world's media.
The implications of Litvinenko's death are enormous. If Putin and the FSB are to blame, they stand accused of murdering a British citizen on British territory: Litvinenko was awarded citizenship only last month. His death has also raised deep concerns about the behaviour of Russia and its leader at a time when they are striving for acceptance by the international community. Just as significantly, it has reminded Britain of the destructive potential of the explosive ongoing feud between the Russian state and its oligarchs-in-exile - most particularly between Putin and his former ally, and now most powerful foe, the billionaire Boris Berezovsky. Worse, this deadly, high-stakes game is being played out on the streets of London.
If Putin was minded to order the bumping off of Aleksandr Litvinenko, the target gave him plenty of reasons to go through with it. Like so many people who had left over the centuries before him, the former spy refused to remain silent about Mother Russia once he had gone. Among his claims were that the KGB trained Bin Laden's deputy Ayman al-Zawahiri; that Italian prime minister Romano Prodi was a Soviet agent and, most explosively, that the Russian government ordered the Moscow apartment bombings in 1999 to justify the second war in Chechnya. He also recently penned an article alleging Putin is a paedophile.
This stream of claims was met by a series of legal actions against the former spy, and official attempts to force British authorities to return him to Moscow. It was a familiar long-distance argument that did not appear to carry any threatening overtones.
That said, all regimes, authoritarian and democratic, have been known to take steps to muffle such dissent in similar circumstances. Russia is accustomed to using the most inventive and brutal methods at its disposal. "Punishing former officers who are considered to have betrayed the service is common to all," said Sean McGough, an intelligence expert at Birmingham University. "The Russians bump them off if they feel that they can get away with it; the Americans lock them up for life under terrible conditions - but may have bumped off a few as well. The Brits pursue them to the ends of the earth with legal actions and destroy their jobs."
The exact details around how Litvinenko met his end remain unclear. It was only three hours before his death that doctors at last identified the toxic substance that was killing him - Polonium-210, a radioactive element used as a trigger in nuclear weapons. Police then discovered traces of Polonium at Itsu, a Japanese sushi bar where he had eaten with a contact on November 1, at the four-star Millennium Hotel in Mayfair where he had met another contact that day, and at the north London home he shared with his wife and 10-year-old son.
Whatever happened in the swanky hotel bar where Litvinenko sipped tea, or the sushi restaurant where he finished a bowl of soup, it is commonly agreed that his involvement in the world of Berezovsky and the oligarch's London-based war on Vladimir Putin placed him in clear danger and contributed to his brutal demise.
Litvinenko had once been ordered to kill the fabulously wealthy Putin ally who fell out of favour with the leadership, and this was one of the reasons he walked out on the FSB. He eventually found himself living in a London house owned by Berezovsky and, critics maintain, doing the oligarch's bidding. Increasingly during Putin's reign, London has become home to the men topping Moscow's Most Wanted list. Above all are Berezovsky and Chechen rebel leader Akmed Zakayev, but also a clutch of former top executives from the oil company Yukos, whose founder, Mikhail Khodorkovsky, was sent to a Siberian labour camp by Putin last year.
Berezovsky is by far the most controversial character. He was one of Russia's first billionaires, an oligarch whose power transcended business and politics. Nicknamed the "kingmaker", he took the credit for installing Putin in the Kremlin in 2000 as replacement for the ailing Boris Yeltsin. But once in office, Putin turned on Berezovsky, who fled to London when prosecutors investigated him for fraud.
Since then he has led a vociferous campaign against the Kremlin from his Surrey mansion. As early as 2001, Russian newspapers claimed Berezovsky was planning an "autumn information attack" against Putin, highlighting his political incompetence, his KGB past and present violations of human rights and "compromising materials" - reports about new presidential residences and his tours of skiing resorts. Oleg Sultanov, a Russian journalist who penetrated Berezovsky's empire in exile, claims he was commissioned by the tycoon to write a book on Putin's Russia, with the clear demand that it should be "as scary as possible".
"It was meant to be some kind of 'foundation study' of the horrors of contemporary Russia and the criminal role of the special services," Sultanov recalled. "After all, that is the core of Berezovsky's theory: the special services, and Putin the former KGB agent, are responsible for everything that's happening in Russia - all the contract murders, terrorist attacks, frauds."
Litvinenko clearly saw common ground with his countryman, not least their then-indeterminate national status. "Berezovsky and me have similar notifications - the so-called 'blue form' that stands for political asylum," he said.
"We are granted virtually all rights of citizens of Britain save for two. We cannot vote and cannot use the green corridor when we fly into Britain."
Whether by accident or design, Litvinenko became part of the "information attack" on his former leader. He relished a platform to deliver his own fiercely critical running commentary on the Putin regime, but his intelligence, even his name, was also used by Berezovsky.
The most dramatic example of their collaboration was the publication of the book Bombing Russia, constructed around the astonishing claim that the security services had planned and executed the apartment bombings which led to war in Chechnya.
Sultanov insists the book was a key element of the Berezovsky campaign against Putin. "First there was the documentary: An Assault On Russia; then the book by Litvinenko the defector; the next link in this chain was meant to be my 'epic'," he said. "Alex Goldfarb, Berezovsky's closest ally, admitted the Litvinenko books were a flop. So it's urgently necessary to create some hot new reading material which would prove that 'our cause is just' and Putin is the enemy of the human race."
Whatever the truth, Putin was every inch the world statesman as he gave his first response to Litvinenko's death, during a summit with the European Union in Helsinki on Friday evening. "The death of a person is always a tragedy, and I convey my condolences to those close to Mr Litvinenko," said the Russian leader, adding: "I hope that the British authorities will not encourage political scandals that do not have real grounds to be blown up, whatever they are."
The thinly-veiled warning is in line with a desire to protect the image not just of Russia but of his beloved security services. That security apparatus has played a key part in restructuring Putin's Russia into a state over which he can wield autocratic power. The president has created a tightly-ordered structure in which all Russia's elites have been guaranteed an economic stakehold. Ultimate power - and overall economic wealth - however, is concentrated in the hands of the state.
Even the lowest-ranking security officials have a stake, as members of the 'siloviki', the four million policemen, soldiers and other elements of the 'securocracy', alleged effectively to hold a licence to exploit - as well as protect - members of the public. Above them are the traditional bureaucrats and at the apex of Putin's pyramid are the 'Barons' - 12 senior ministers and Kremlin courtiers, all close friends of the president.
Where only a decade ago Berezovsky said only seven oligarchs controlled Russia's newly privatised economy, now seven of Putin's barons head public companies accounting for 40% of the nation's wealth. Critics of the Putin regime claim he has simply replaced the oligarchs and the feared Russian mafia with this feudal state apparatus designed to operate its own rackets and cream off its own share of the profits of legitimate business.
Russian officials are genuinely puzzled by the British attitude to the exiles, not least Berezovsky, the Tsar over the water. But while London gives them a home and fiercely resists repeated Russian attempts to extradite them back to their home country, it is also taking pains to rein them in.
When, earlier this year, Berezovsky advocated the violent overthrow of Putin, the then-foreign secretary Jack Straw told him to shut up, saying his refugee status might otherwise be reviewed. And just this month, Moscow's deputy prosecutor general Alexander Zryagintsev was invited to London to sign a memorandum of understanding that British officials say will make it easier for Moscow to win extradition cases. Zryagintsev confirmed that extradition cases for Berezovsky and Zakayev remain "on the table."
That wasn't enough to save Litvinenko. But then, in this murky world of claim and counter-claim, the truth about his death may never be known. Putin's opponents have been quick to pin the blame on the FSB, the successor organisation to the KGB, but the truth may be more complicated. Even the shocking official proof of a KGB-style poison in Litvinenko's body will not necessarily implicate the security services - and certainly not Putin himself.
Luke Martin, an expert in Russian politics at Edinburgh University, pointed out that the Kremlin is currently involved in a fierce struggle between powerful barons over who will succeed Putin as president in 2008. "I can't see how this would help them," he said. "And I can't believe Litvinenko would have been regarded as a serious enough threat to merit an officially-sanctioned assassination."
Philip Davies, deputy director of the Brunel Centre for Intelligence and Security Studies, suspects any official involvement in the killing would effectively have been on a "freelance" basis. "It is more likely to be a third party, either something like the Russian mafia or a piece of political private enterprise pursuing the Russian government's opponents," he said.
Whoever killed Litvinenko, the effect on Russia's exiles will be the same fear that was felt after the murder of Russia's leading journalist Anna Politkovskaya. A fierce critic of Putin, who was once unsuccessfully poisoned, she was eventually shot dead outside her apartment last month. Rather than a punishment for any of his own deeds, Litvinenko may have been sacrificed 'pour encourager les autres' - particularly the troublesome and turbulent Boris Berezovsky.
Within Russia, loyal politicians prefer to point the finger of guilt at the arch oligarch himself. Gennady Gudkov, a retired FSB officer and member of the state duma's security committee, said Litvinenko had fallen victim to internal strife among Berezovsky's close associates or, still more probably, to struggle for control of cash flows.
The headache for British investigators is that, for whatever reason, someone with powerful resources, and access to lethal poisons has apparently decided London is no longer off-limits for assassination.
Additional reporting: Chris Stephen and Murdo MacLeod
A brief history of assassinations
Archduke Franz Ferdinand: The killing of the heir to the Austrian throne in Sarajevo in June 1914 triggered the First World War. Gavrilo Princip leapt from the crowd, shot the prince and his wife dead, and consigned Europe to four years of warfare.
Reinhard Heydrich: An SS general regarded as a potential successor to Hitler, Heydrich was placed in control of Czechoslovakia during the Second World War, where he was targeted by British-trained Free Czech agents. He died from blood poisoning from injuries sustained after a bomb attack.
Black September: Members of the Palestinian group that killed 11 Israeli athletes during the Munich Olympics in 1972 were methodically hunted down by Mossad. Operation Wrath of God saw assassinations in Rome, Cyprus, Paris, Beirut, Athens, Rome and Norway.
Georgi Markov: The Bulgarian dissident and broadcaster had already survived two failed attempts on his life when he was attacked while waiting for a bus in London. He was jabbed in the leg with an umbrella held by a man who apologised in a foreign accent and walked away. Markov developed a fever and died three days later. A post-mortem examination revealed traces of ricin toxin from a pellet in his leg.
Fidel Castro, left: The United States' reviled neighbour has survived up to 600 CIA-backed attempts on his life, including exploding cigars, a toxic dose of LSD, a cyanide milkshake and a wetsuit contaminated with tuberculosis. The most outrageous allegation is that the US planned to put chemicals on Castro's shoes to make his trademark beard fall out and expose him to ridicule.