You would be hard put to find better cover to assassinate an exiled Russian dissident. On Wednesday, November 1, hundreds of Russians were in London to watch Arsenal play CSKA Moscow in the Champions League. Among all the families, groups and individual supporters arriving from Moscow, a killer, or killers, could hope for anonymity.
After the evening kick-off at the spectacular new Emirates stadium in north London, Arsenal wasted three good chances on goal. The match ended in a draw. Elsewhere in the capital, however, someone had struck with lethal accuracy.
That evening in Muswell Hill, a little north of Arsenal, Alexander Litvinenko, a former Russian spy and enemy of Vladimir Putins regime, became ill and began vomiting.
Within days he was in hospital; by November 23 he was dead, his internal organs destroyed by a rare radioactive isotope called polonium-210.
This murder and it looks increasingly like a cunning, ruthless murder has sparked a huge police investigation that has uncovered radiation at 12 sites across London and on two British Airways planes that had flown between London and Moscow.
British Airways has had to warn 33,000 passengers who travelled on flights in the contaminated planes. Thousands of people have contacted the NHS, worried that they may have come into contact with polonium.
Though the risk to their health is said to be minimal, the chief medical officer was impelled to warn doctors that the symptoms of poisoning from tiny amounts of polonium might not appear for up to four weeks, a deadline that ran out last week.
The affair also threatens a diplomatic crisis as accusations fly that the Russian security service, or rogue elements of it, are behind Litvinenkos death. It has prompted statements in parliament and hurried meetings of Cobra, the government committee that handles emergencies.
The cabinet was briefed about the affair on Thursday. According to authoritative sources, John Reid, the home secretary, described Litvinenkos background in the Russian security service and also said he had been involved with organised crime as have many former Russian security personnel.
Reid said about 20 sites more than publicly admitted were being investigated for radiation. Ministers were warned there was a danger of the health system being overloaded. Ministers were also told that Russia had complained about the publication of a deathbed statement by Litvinenko, blaming Putin for his killing.
Tony Blair told ministers his prime concern was the damage the Litvinenko affair might do to relations with Russia. The most important thing, Blair told cabinet, was to manage the relationship with Russia.
For if the case of the poisoned spy is down to a foreign assassin it is an unprecedented nuclear attack on British soil. There is a temptation for those concerned with the political fallout to clutch at alternative scenarios to a killing by a Kremlin hitman.
A senior Scotland Yard source said yesterday that investigators are closing in on a suspect. Hunting with radiation detectors, the police have been painstakingly reconstructing Litvinenkos movements on November 1, trying to identify where he went and who he met.
Late last week police were still working behind a sealed-off part of the eighth floor of the Sheraton Park Lane hotel after finding traces of polonium.
They were investigating a Russian guest whose room had shown signs of contamination before November 1. If so, it would be a strong clue to the origins of the polonium.
The police were giving nothing away about the identity of their target. But The Sunday Times has established that a former Russian agent called Andrei Lugovoi, who was known to Litvinenko, stayed in the hotel in the days before November 1 and that he is he says significantly contaminated with polonium.
Litvinenkos close friends believe Lugovoi is deeply involved, either knowingly or unknowingly, in the poisoning. But Lugovoi and his business partner, Dimitri Kovtun, who also visited London, vehemently deny involvement and say they have been set up as fall guys.
Lugovoi has claimed: Traces were found even on my children and on my wife. To think that I would handle the stuff and put them at risk is simply ludicrous.
Though it remains hedged in murk and mystery, a few firm findings are emerging from the fog of conspiracy theories. They include:
Polonium-210 of the quantity and purity used to kill Litvinenko is difficult to obtain, and cannot simply be ordered over the internet. The amount used, more than 100 times a lethal dose, implies it was obtained either from a reactor or in an unusually large commercial transaction that would have raised eyebrows.
Though some polonium is imported into Britain, no polonium is made here and none has been reported missing. This indicates that the isotope was smuggled into the country.
Litvinenko was contaminated on November 1 and not before. Yet it is thought traces of polonium on a plane and in a London hotel date from October 25.
Police have identified a trail of polonium residues at 12 sites across London, including a restaurant, two hotels, some offices and Litvinenkos home.
So far only Litvinenko, his wife Marina and Mario Scaramella, an Italian who met Litvinenko on November 1, have tested positive for absorbing polonium into their bodies. Marina and Scaramella have far lower levels of contamination than Litvinenko suffered and as yet are reportedly showing no ill-effects.
THE more that emerges about Litvinenkos death, the more polonium is revealed as an extraordinary weapon for assassination. Though it leaves a radiation trail, this is of usually benign alpha particles that do not register on normal geiger counters. The assassin or assassins may have gambled it would never be detected.
There are three basic types of radioactive particles or rays: alpha, beta and gamma. Gamma are generally regarded as the most deadly because they are a powerful penetrator of solid objects. Alpha radiation, on the other hand, can be stopped by something as thin as a piece of paper or skin.
As far as I know this is the first person ever to have died of an overdose of alpha radiation, said Nick Priest, the former head of biomedical research at the Atomic Energy Authority. I cant think of any other case where a lethal dose has been administered by alpha radiation.
Only if a substance emitting alpha particles gets inside the body and dissolves into the bloodstream does it slowly wreak havoc.
This is why doctors treating Litvinenko when he fell ill were baffled. He exhibited classic signs of radiation poisoning, including vomiting, hair loss and organ failure. But when they tested for gamma radiation with a geiger counter, they found nothing unusual.
The police who interviewed Litvinenko in hospital initially did not know what had caused his illness and had little to go on. There was no trail to follow.
The Health Protection Agency (HPA), a body that merged with the National Radiological Protection Board in 2005, was out of its depth. Polonium is so rare that nobody thought to look for it.