Mr Berezovsky, a former maths professor, made his millions in the 1990s when he bought stakes in the Russian car, oil and media industries, many of which he sold off for enormous profits. He lives with his fourth wife in a Surrey mansion but has an office at the Mayfair address.

Detectives were also searching the offices of a security and risk management company in Grosvenor Street, in the West End of London, where traces of polonium 210 have been found. A spokesman for the company, Erinys, said it had alerted police because Mr Litvinenko had visited its offices on a "totally unrelated" matter some time before he was admitted to hospital. He added: "None of our staff with whom he had contact have suffered any ill effects."

The development came as the Health Protection Agency (HPA) said three people had been referred for further radiation tests at a special clinic after contacting NHS Direct in the past few days. They were among 18 people referred to the HPA for possible further examination since the radiation alert was issued on Friday.

In the past four days around 500 people have contacted NHS Direct saying they were concerned they may have been contaminated after visiting the Piccadilly restaurant Itsu or the Millennium Hotel in Grosvenor Square on November 1, the day Mr Litvinenko first became ill.

Dr Pat Troop, the chief executive of the HPA, said people referred to the specialist clinic would undergo urine tests for radioactivity over the next couple of days. The decision to refer them for tests was taken on "a very precautionary basis", she stressed. Further tests might be carried out if police identified other locations of concern.

Dr Troop said the HPA had not precisely identified when and where Mr Litvinenko ingested the poison. Working out the time of poisoning on the basis of radioactivity found in his body was "not a precise calculation", she said.

In a statement to the House of Commons, the home secretary, John Reid, stressed that police had yet to open a murder inquiry. He warned against any speculation about the death and said the police were not yet saying that Mr Litvinenko had been unlawfully killed. "The police have been very careful in the words they have used; they are dealing with a suspicious death," he said. "We are not yet at the stage that there is definitely a third party involved."

Mr Reid's statement came in response to an urgent question from the shadow home secretary, David Davis, who said in the House of Commons that there were grounds to suspect that this was a "a particularly cruel, protracted and unpleasant assassination".

Mr Davis said the apparent use of polonium 210 raised "a number of issues" over how such material had been obtained, how it was transported and delivered undetected, and who had the knowledge to use it.

Mr Reid said there were 130 premises in England and Wales with a known use of polonium 210, each regulated and controlled by the Environment Agency. "There has been no recent report of the loss or theft of polonium 210 in England and Wales," he said.

Mr Reid drew back from Peter Hain's outspoken criticism of the Kremlin at the weekend. The Northern Ireland secretary had strained Britain's relations with Moscow further by accusing President Putin of "huge attacks" on liberty and democracy.

Tony Blair and President Putin are due to meet this week at the Nato summit in Riga, Latvia. A spokesman for Mr Blair said yesterday: "The prime minister and other ministers have repeatedly underlined our concerns about some aspects of human rights in Russia. In terms of this particular case, however, we do have to proceed carefully."

Mr Litvinenko, an ex-KGB officer and vocal opponent of Mr Putin, died last Thursday night. A large dose of alpha radiation from the isotope polonium 210 was found in his urine. A statement he composed before he died blamed Mr Putin, a claim denied by the Kremlin.

The inquest into the death is expected to open on Thursday at St Pancras coroner's court, north London. It will be adjourned until a later date. Dr Andrew Reid, London's inner north district coroner, has to decide if and when to conduct a postmortem examination.

He described the nature of his relations with Litvinenko. "We knew each other about 10 years before he moved to London. We were just acquaintances and did not maintain any personal or business relations. We had a period where we did not see each other and roughly a year ago he called me from London and asked whether I would visit London and I accepted the invitation as I have certain interests in London.

"He proposed to meet as he had an offer to make that he said could interest me. We met and he helped to establish business relations with several respected British companies. I gave their names to the British embassy to make the situation as transparent as possible. Over the past 12 months we met each other solely to discuss business matters since I was conducting dialogue with the British companies interested in investments in Russia. We negotiated an agreement about certain consulting on the matters in Russia," Mr Lugovoi said.

He found nothing special in Litvinenko's behavior during the meeting on November 1. "There were no signs he was ill, he was quite optimistic and behaved as usual. I did not notice anything special which drew attention. The meeting on November 1 in a London Millennium Mayfair hotel was rather short - no longer than 20-30 min and was not confidential. It was on Litvinenko's initiative and I even asked to shift it to November 2. I was in London for a single purpose to show the city to my family. I was in the UK also with my two business partners Vyacheslav Sokolenko and Dmitry Kovtun to attend a football game CSKA vs Arsenal and to rest. That's it," the Russian businessman added.

He refrained from speculating on Litvinenko's death. "It's a complicated question. I'd be very careful with any statements since the subject is very sensitive. The investigation can actually answer the question of what really happened. There should be proper diagnostics and checks which either proves the poisoning or not. The developments around Alexander within the last three weeks as far as his health deterioration is concerned are very strange, but I'm really surprised with the hysterical attempts to link me up to the events around Alexander," Lugovoi pointed out.

He dismissed the allegations in the Western media concerning his involvement. "After November 1 I was in London for 2 more days and did not go away suddenly as it was reported in the Western media. Secondly, we agreed with Alexander to meet each other in November in Madrid, where I planned a vacation with my wife. As Alexander learnt it he told me he knows a Spanish businessman interested in establishing contacts in Russia. He asked me to meet that man.

"Litvinenko and I agreed to contact each other to discuss the details. I called him on November 7 and he told me he felt sick, as if he had been poisoned. And one more thing - he called me up in London on my mobile phone on November 2 at 20-00 and asked to postpone the planned meeting. Then he called me in the evening and we agreed to stay in touch.

On November 7 we had a phone conversation and he told me he had been unconscious for two days and then felt better and hopes to be discharged soon. His wife Marina was present during the conversation. We agreed to have a conversation in a week. I called him on November 13 after first publications where he claimed to have been poisoned and I declared my sympathy to him. I told him I will probably be in Spain in November, exactly November 23, but he replied his condition had deteriorated and he will not be able to meet me and perhaps we will meet in December. All the people around him knew we met on November 1 and had calm conversations on November 2, 7 and 13. Last time we agreed to call each other in a week," Lugovoi explained.

He said he demonstrated a transparent position on Litvinenko's case and continues to stay in contact with the UK authorities.

"I returned to Russia on November 20 late in the evening. My friends called me and told me my name is mentioned in connection with this case. I rushed to the office, looked through the Internet. Next day I contacted the UK embassy and asked for a meeting to clarify the situation and possibly help the investigation and demonstrate the transparency of my position taking into account the fact I have business interests in the UK and my partners there have business interests in Russia.

"We agreed to meet on Thursday at 2 pm. I was there with Dmitry Kovtun who purely by accident was present at the meeting with Litvinenko on November 1. We exchanged views with UK representatives and agreed to meet the British police and clarify the situation. We had another conversation today and I expect the information on the procedure - will it be in the UK or the police officials will come here. I will also seek the advice of my lawyer. Immediately after the meeting in the UK embassy I contacted the media to represent my view as I consider any statements before such a meeting incorrect. Now I'm free to comment and open for contact," Russian businessman concluded.

Mario Scaramella, who has advised an Italian parliamentary commission on Soviet-era espionage, is being checked to verify whether he too has been contaminated.

"He went to London and is under British protection. He is undergoing medical tests to determine his possible contamination," said the Rome-based source, who asked not to be named.

Here is one typical paragraph. Barnett says that Litvinenko was poisoned with thallium, which "a well-placed security source" tells him "suggests a state actor, and one with a long-standing interest in assassination techniques". Barnett goes on: "Poisoning a British citizen on British soil demonstrates a new level of chutzpah even for the Putin regime (which, for the record, rejects any links to the attack as 'sheer nonsense')".

Firstly, Litvinenko wasn't poisoned with thallium. That suggestion came from John Henry, a toxicologist who was approached by the office of Boris Berezovsky to give his opinion on the case, and who readily did so, despite not yet having seen the test results of Litvinenko. He later withdrew his comments.

Nonetheless, Barnett's "well-placed security source" uses this faulty testimony to conclude that a state actor must be involved - in other words, the Kremlin. How well-placed a security source can he be if he doesn't even check his basic facts before immediately and publicly pointing the finger at Putin?

From this speculation based on faulty testimony, Barnett has already concluded that the Putin regime is responsible. He gets indignant over the fact the attack was on a British citizen, though he doesn't mention the strange coincidence that Litvinenko only became a British citizen on the very day he was poisoned.

Barnett makes no mention of the fact the Kremlin stands to lose a lot more than it gains from Litvinenko's killing. He does not mention that it occurred just as Putin was attending a sensitive and important EU-Russia summit in Helsinki, and that this summit was far more important to Russian national interests than some played-out ex-spy who had already said everything he had to say. He does not mention that Litvinenko's death was long, drawn-out and spectacular - in other words, guaranteed to attract maximum media attention, which is directly against the interests of the Russian government. He does not mention that Anna Politkovskaya's killing likewise coincided with another sensitive international visit of Putin's, which it likewise managed to sour. These are basic facts of the case, obvious points which cast doubt on the Kremlin's motive. But they are not mentioned at all.

He gets other basic facts wrong. He goes on the usual anti-Kremlin rant, blaming it for scaring foreign investors and undermining 'BP's contract in Sakhalin'. Anyone who covers Russia at all regularly knows it is Shell's contract in Sakhalin, not BP's. A trip to Barnett's website shows he has barely written on Russia in the last few years, and is basically a Balkans expert. Good for him - but in that case, how can he be so certain that the Kremlin is to blame, and that it isn't being set up?

Like many other British articles, Alexander Litvinenko becomes in Barnett's description a Stoic hero. Barnett pays tribute to the "boyish charm" of the man who by his own admission happily worked for the FSB recruiting killers and blackmailing businessmen before he jumped ship to work for Boris Berezovsky in the UK. How did he manage to conquer his fear to stand up to the FSB, asks Barnett gushingly. Simple - Boris Berezovsky offered to pay him more.

Berezovsky himself has become heroic in British media reports. He is, in Barnett's description, a "dissident oligarch", as if he was some kind of Solzhenitsyn, gracing our shores with his moral courage. Only the smarter journalists are beginning to notice how totally Litvinenko's death has been manipulated by Berezovsky - press briefings were handled by Alex Goldfarb, described as a "friend and human rights expert" by British press. Goldfarb is actually Berezovsky's right-hand man, which tells you all you need to know about his respect for human rights.

The press were also fully briefed by Lord Tim Bell, a British spin-doctor who has worked with Berezovsky for many years. He told the Financial Times that "anyone who knew his client knew he would be incapable of killing anyone". Anyone who is familiar with 1990s politics in Russia, and who has read the murdered journalist Paul Klebnikov's book about Berezovsky, Godfather of the Kremlin, knows what a ridiculous and disingenuous statement that is. What is Tim Bell doing working for Berezovsky? Is anybody's money good enough for him?

It's not just the media that appears happy to take the bait. Our own government has been joining the fray. This weekend, Peter Hain, the Northern Ireland minister, saw fit to wade in and throw mud at Putin, on British national TV, for "huge attacks on democracy", and the "extremely murky murder" of Anna Politkovskaya. If the murder is extremely murky, how does he know Putin ordered it? How can a British minister be so irresponsible as to accuse the president of Russia of murder, when he doesn't have any evidence, considering the huge investments British companies have made in Russia, and the huge importance of Russia as a trade and security partner?

The fact that Hain is himself fighting for his political career, as a British judge accused him this month of perverting the course of justice in his work as Northern Ireland secretary, is of course by-the-by - we'd much rather hear him talk about Russian internal politics than answer questions about that particular investigation.

Luckily, more experienced journalists, ones actually based in Russia, are making more sensible comments. Mark Franchetii, the seasoned Sunday Times correspondent here, wrote a piece quoting a senior Kremlin source who pointed the finger at Berezovsky. Catherine Belton likewise noted, in today's Moscow Times, that Litvinenko's death seemed highly stage-managed. I also spoke a senior editorial figure from Kommersant (I can't give his name because it was a social occasion and he didn't know I was a journalist) - he said he thought it was Berezovsky, and he'd been employed by Berezovsky for several years.

Like I said, the common sense and integrity of British journalism and British politicians are on trial here. We should be extremely careful we are not being taken for a ride, and taking our own public for a ride at the same time.