THE Russian community in London has until recently been regarded by the natives with wry amusement. The exiled tycoons and billionaire tax refugees at its centre have boosted the price of high-end houses, imported expensive football players along with their befurred wives and provided useful fodder for the gossip columnists. But Russian visitors have also brought political intrigue, business grudges, shady pasts— and, apparently, polonium.

That was the radioactive substance used to poison Alexander Litvinenko, who before defecting to Britain worked for both the KGB and the FSB, one of the KGB's post-Soviet successors. Mr Litvinenko died in a London hospital on November 23rd, having fallen ill on November 1st. On that day, he met Mario Scaramella, an Italian muckraker who has investigated the KGB's activities in Italy, at a Piccadilly sushi bar, and two or more visiting Russians (also ex-KGB) at a posh London hotel.

On December 7th, as Mr Litvinenko was buried in London, it emerged that several staff at the hotel bar had shown traces of radiation—making it a likely scene of the crime—as have rooms at several establishments in which the visiting Russians stayed, and planes on which they flew between London and Moscow. So has part of the British embassy in Moscow, which the Russians attended to explain themselves. German authorities have also detected radiation at several sites in Hamburg that one of the Russians, Dmitri Kovtun, visited before the fateful hotel meeting with Mr Litvinenko, suggesting that Mr Kovtun was already contaminated before they met.

As well as the flying KGB men, the Litvinenko affair now encompasses a long cast of characters, some of whom may be accomplices or escaped co-targets or the stooges in frame-ups. This melange has predictably produced an orgy of conspiracy theories, some of which are probably smears and disinformation, circulated by people who have taken Mr Litvinenko's demise as a grand opportunity to discredit their enemies.

The initial, rushed assumption among many in London was that the Kremlin did it—or if not the Kremlin directly, the FSB; or if not them, then former KGB/FSB men. (Vladimir Putin, another former spook, himself once reputedly remarked that there is no such thing as ex-KGB men). Many in these organisations reviled Mr Litvinenko, who accused the FSB of various crimes. One of his allegations was that the FSB orchestrated a spate of mysterious bombings of Russian apartment blocks in 1999, which contributed to the eruption of a new Chechen war and hence to Mr Putin's election as president in 2000. Several others who have investigated the bombings have wound up either dead or in prison. Some see Mr Litvinenko's death as part of sequence of recent murders that included the contract killing in October of Anna Politkovskaya, a crusading journalist and devout Kremlin critic.

The main rival version propagated by the Kremlin's allies is that the Litvinenko poisoning and Politkovskaya shooting were instead the work of forces bent on discrediting Mr Putin. This version generally tries to implicate Boris Berezovsky, a so-called oligarch who helped bring Mr Putin to power but then fell out with him and fled to London. Mr Litvinenko claimed that, as an FSB officer, he had been ordered to kill Mr Berezovsky; the tycoon became his sponsor when both were in London. Yegor Gaidar, a former Russian prime minister who thinks he was himself poisoned in Ireland on the day Mr Litvinenko died, believes that his own ailment was part of such an effort, though Mr Gaidar has not publicly named any names.

But there are other theories, including the idea that Mr Litvinenko's murder—as it is now officially classified by Scotland Yard detectives—is somehow part of an ongoing power struggle inside the Kremlin, in advance of Mr Putin's putative departure from office in 2008. There are several sub-theories: that the point is to undermine one or other of his possible successors, or somehow to force Mr Putin to stay in office, which some who have profited during his presidency would like. Then there is the theory that Mr Litvinenko was himself hawking the polonium around London to potential buyers, or (so say some in Moscow) had been helping Chechen terrorists to build a “dirty bomb”. Or that he had fallen foul of Russian gangsters, who are not always easily distinguishable from the government. And so on.

Cui bono?

The scandal has arisen at a time of already increased tension between Russia and Britain, partly induced by Britain's refusal to extradite Mr Berezovsky. Sergei Lavrov, Russia's foreign minister, has given warning that it threatens to make Anglo-Russian relations even worse. The Kremlin was said to be angry that accusations Mr Litvinenko supposedly made against Mr Putin from his deathbed were publicised. The Russians apparently misconstrued the police protection given to Mr Litvinenko in hospital as some sort of incarceration.

Reuters

Mourning Anglo-Russian relations?

Realising the damage that is being done to the reputation of Russia and Russians, the Kremlin has been trying to appear co-operative with the team of British detectives who arrived in Moscow on December 4th. Yet the co-operation will be tightly circumscribed. Yuri Chaika, Russia's attorney-general, said that the British officers would be allowed to make no arrests nor question witnesses directly. It is almost inconceivable that anyone could ever be extradited. Serving or former FSB officers are unlikely to be questioned. One, Mikhail Trepashkin, claims to have useful information. But, like Mr Litvinenko, Mr Trepashkin has investigated the 1999 apartment bombings. He is currently in prison in the Urals.

The Russians, meanwhile, have begun their own investigation into Mr Litvinenko's death and Mr Kovtun's alleged poisoning. That is as likely to result in as much obfuscation as elucidation: whoever is guilty, the Russian reflex—as, for example, the Kursk submarine disaster in 2000 and the Beslan school massacre of 2004 prove—is to cover up and prevent any blame sticking anywhere important. With their Russian colleagues, the London detectives managed to speak to Mr Kovtun, but as of December 7th had yet to interview Andrei Lugovoi, an associate of Mr Kovtun who met Mr Litvinenko several times in the month before his death. Mr Lugovoi protests his innocence.

The polonium may be the most important clue, though it has various possible implications. One is that the choice of a radioactive poison was intentionally sensational. If so, it was designed either to demonstrate the scope and ruthlessness of the murderers, and to send a hair-raising message to Mr Litvinenko's friends and hosts. Or—according to another rationale—to damage Mr Putin's reputation and Russian-Western relations.

Alternatively, whoever chose it may have thought that it would have been untraceable. Instead it left a radioactive trail that is helping the British police decipher where and by whom it was given to the victim. But even if the assassin is identified, the ultimate authors of the crime are very unlikely to be.