You can watch the full video of Lugovoy's press conference here

During his press conference, Mr. Lugovoy put forward a theory about Mr. Litvinenko's death - that the ex-Federal Security Service officer was murdered in revenge for cooperating with Spanish police in the late 1990s to bring down Zakhary Kalashov, who was then a powerful figure in the Russian underworld. One of Mr. Kalashov's former associates has dismissed the accusation as "a fairy tale".

Dimitry Kovtun works with the Moscow security company Devyatyy Val (9th Wave). The KGB's ninth (Guards) department was responsible for protecting VIPs in the Soviet Union. After 1991 it was replaced by the Federal Protective Service (FPS)

There is no doubt that Litvinenko made many enemies while working in the Russian Federal Security Service (FSB)'s elite counter-organized crime unit, particularly after he befriended Boris Berezovsky in the mid-1990s. At that time, Mr. Berezovsky was the richest man in Russia and boasted about his influence over President Yeltsin's inner circle. Berezovsky was widely despised by many members of the security services, who viewed him and his fellow oligarchs as criminals who were impoverishing Russia. When the future President Putin became director of the FSB in 1999, Litvinenko was dismissed from FSB and charged with corruption and misappropriating department resources. During this same time period, Berezovsky employed an ex-KGB bodyguard named Andrey Lugovoy to run security for his ORT television network.

At the press conference Mr. Lugovoy was accompanied by Dimitri Kovtun, the other Russian businessman who met Litvinenko in London on November 1, 2006. For his part, Kovtun claimed that Litvinenko bragged to him about alleged plans to blackmail Boris Berezovsky and other Russian oligarchs. Kovtun also claims that Litvinenko discussed his work as an intermediary between Chechen separatists and Ahkmed Zakayev, their spokesman in London. Kovtun added that Litvinenko confided in him that he had travelled to the Pankisi Gorge, an area where U.S., Russian, and Georgian special forces have hunted international jihadists.

Former KGB officer Mikhail Lyubimov: "All of these guys are crooks"

Mikhail Lyubimov, a veteran KGB officer who is now a writer on intelligence issues, has dismissed all of the claims surrounding the case, ""All of these guys - the deceased Litvinenko, [Berezovsky] and Lugovoy - are crooks and should not be taken seriously." A senior Russian government source echoed this view. Speaking on condition of anonymity to Russia's Kommersant newspaper ("Lugovoy Gives his Version of Events") , the source dismissed Lugovoy's allegations as nonsense taken straight out of spy novels.

Although Russian prosecutors have charged Chechen separatist spokesman Ahkmed Zakayev with sponsoring terrorism, there is no evidence that his "good friend Sasha" Litvinenko ever travelled to Georgia after leaving Russia for good in 2000. However, a spokesman for the FSB has said that the agency is looking into Mr. Lugovoy's allegations.

Regardless of the very questionable backgrounds of Mr. Litvinenko's associates, most Western media commentators have already made up their mind about this bizarre case - Litvinenko, they argue, must have been killed by his former colleagues in the FSB. A dying man - even one who was allegedly running low on money with a surviving spouse - supposedly has no reason tell a lie on his death bed. But in my view, this kneejerk version of events is more comforting to most Westerners than another disturbing possibility - that Litvinenko was the first victim of nuclear terrorism (or botched polonium smuggling) that the world has ever seen.

UPDATE - July 5, 2007: Russia has rejected Great Britain's request for Mr. Lugovoy's extradition.