This week, the inquiry into the death of Alexander Litvinenko will deliver its findings. The former Russian spy was poisoned with a cup of tea in a London hotel. Working with Scotland Yard detectives, as he lay dying, he traced the lethal substance to a former comrade in the Russian secret service

The Millennium hotel is an unusual spot for a murder. It overlooks Grosvenor Square, and is practically next door to the heavily guarded US embassy, where, it is rumoured, the CIA has its station on the fourth floor. A statue of Franklin D Roosevelt – wearing a large cape and holding a stick – dominates the north side of the square. In 2011 another statue would appear: that of the late US president Ronald Reagan. An inscription hails Reagan’s contribution to world history and his “determined intervention to end the cold war”. A friendly tribute from Mikhail Gorbachev reads: “With President Reagan, we travelled the world from confrontation to cooperation.”

The quotes would seem mordantly ironic in the light of events that took place just around the corner, and amid Vladimir Putin’s apparent attempt to turn the clock back to 1982, when the former KGB boss Yuri Andropov – the secret policeman’s secret policeman – was in charge of a doomed empire known as the Soviet Union. Next to the inscriptions is a sandy-coloured chunk of masonry. It is a piece of the Berlin Wall, retrieved from the east side. Reagan, the monument says, defeated communism. This was an enduring triumph for the west, democratic values, and for free societies everywhere.

Alexander Litvinenko: the man who solved his own murder Read more

Five hundred metres away is Grosvenor Street. It was here, in mid-October 2006, that two Russian assassins had tried to murder someone, unsuccessfully. The hitmen were Andrei Lugovoi and Dmitry Kovtun. Their target was Alexander Litvinenko, a former officer in Russia’s FSB spy agency. Litvinenko had fled Moscow in 2000. In exile in Britain he had become Putin’s most ebullient and needling critic. He was a writer and journalist. And – from 2003 onwards – a British agent, employed by MI6 as an expert on Russian organised crime.

Latterly, Litvinenko had been supplying Her Majesty’s spooks and their Spanish counterparts with hair-raising information about the Russian mafia in Spain. The mafia had extensive contacts with senior Russian politicians. The trail apparently led to the president’s office, and dated back to the 1990s when Putin, then aide to St Petersburg’s mayor, Anatoly Sobchak, worked closely with gangsters. In a week or so, Litvinenko was to testify before a Spanish prosecutor. Hence, it appeared, the Kremlin’s frantic efforts to kill him.

The men from Moscow were carrying what Kovtun confessed to a friend was “a very expensive poison”. About its properties he knew little. The poison was polonium-210, a rare radioactive isotope, tiny, invisible, undetectable. Ingested, it was fatal. The polonium had originated at a nuclear reactor in the Urals and a production line in the Russian town of Sarov. A secret FSB laboratory, the agency’s “research institute”, then converted it into a dinkily portable weapon.

Lugovoi and Kovtun, however, were rubbish assassins. The quality of Moscow’s hired killers had slipped since the glory days of the KGB. Their first attempt, in a Grosvenor Street boardroom, had not worked. They had lured Litvinenko to a business meeting, where – the radiation stain later showed – they had tipped polonium into his cup or glass. But Litvinenko did not touch his drink. As of 1 November 2006, he was stubbornly alive.

Lugovoi and Kovtun were rubbish assassins. The quality of Moscow’s hired killers had slipped since the KGB's glory days

Like most upmarket London hotels, the Millennium has CCTV. Its multiplex system can run up to 48 cameras; that day, 41 of them were operational. The cameras work on a time-lapse system. They take an image every two seconds; the video is retained for 31 days. This footage has a jerky quality, a little like the early days of cinema – images jump; people appear and vanish; life ebbs and flows. And yet it is an honest record. A time stamp – days, hours, minutes – fixes everything. The stills offer a miraculous time machine, a journey into verisimilitude.

Even modern CCTV has its limitations. Some parts of the Millennium were not covered by it – as Lugovoi, an expert in surveillance, and a former Kremlin bodyguard, would have noticed. One camera was fixed above the reception desk. Its footage shows the check-in counter; a bank of three computer screens; uniformed hotel staff. In the left of the picture is a part view of the foyer. There are two white leather sofas and a chair. Another camera – you wouldn’t notice it, unless you were looking – records the steps leading up to the lavatories.

The hotel has two ground-floor bars accessed from the foyer. There is a large restaurant and cafe. And the smaller Pine Bar immediately on the left as you enter through a revolving door from the street. The bar is a cosy wood-panelled affair. Three bay windows look out onto the square. In CCTV terms, the Pine Bar is a security black hole. It has no cameras; its guests are invisible.

Facebook Twitter Pinterest Andrei Lugovoi with his two daughters at the reception desk of the Millennium hotel.

On the evening of 31 October, camera 14 recorded this: at 20:04 a man dressed in a black leather jacket and mustard yellow jumper approaches the front desk. On either side of him are two young women. They have long, groomed blonde hair: his daughters. Another figure wanders up from the sofas. He is a strikingly tall, chunky-looking bloke wearing a padded black jacket and what resembles a hand-knitted Harry Potter scarf. The scarf is red and blue – the colours of Moscow’s CSKA football club.

The video captures the moment the Lugovois checked in – on this, his third frantic trip to London in three weeks, Lugovoi arrived with his entire family. He came from Moscow with his wife Svetlana, daughter Galina, eight-year-old son Igor, and friend Vyacheslav Sokolenko – the guy with the scarf. At the hotel, Lugovoi met his other daughter Tatiana. She had arrived from Moscow a day earlier with her boyfriend Maxim Bejak. The family party was due to watch CSKA Moscow play Arsenal in the Champions League the following evening. Like Lugovoi, Sokolenko was ex-KGB. But Sokolenko was not, British detectives would conclude, a murderer.

CCTV shows Kovtun arriving at the Millennium at 08.32 the next day – a diminutive figure carrying a black bag over one shoulder. The events of the next few hours were to become infamous – with Litvinenko the fated victim, the Russian state an avenging god, the media a sort of overexcited Greek chorus. What actually took place was a piece of improvisation that might easily have misfired. Lugovoi and Kovtun had decided to lure Litvinenko to a further meeting. But the evidence suggests that they had still not figured out how exactly they were going to kill him.

Litvinenko had first met Lugovoi in Russia in the 1990s. Both were members of the oligarch Boris Berezovsky’s entourage. Later, while living in exile in London, Berezovsky became Litvinenko’s mercurial patron. In 2005, Lugovoi recontacted Litvinenko and suggested they work together, advising western firms wanting to invest in Russia. At 11.41am, Lugovoi called Litvinenko on his mobile. He suggested a meeting. Why didn’t Litvinenko join him later that day at the Millennium? Litvinenko said yes; the plot was on.

Scotland Yard would later precisely fix Litvinenko’s movements on the afternoon of 1 November: a bus from his home in Muswell Hill in north London; the tube to Piccadilly Circus; a 3pm lunch with his Italian associate Mario Scaramella in the Itsu sushi restaurant in Piccadilly. In between, he fielded several calls from Lugovoi, who was becoming increasingly importunate. Lugovoi called Litvinenko again at 3.40pm. He told Litvinenko to “hurry up”. He had, he said, to leave imminently to watch the football.

Lugovoi would tell British detectives that he arrived at the Millennium at 4pm. The CCTV shows that he was lying: half an hour earlier, at 3.32pm, Lugovoi appears at the front desk and asks for directions to the gents. Another camera, number four, records him walking up the stairs from the foyer. The image is striking. Lugovoi seems preoccupied. He is unusually pale, grim, grey-visaged. His left hand is concealed in a jacket pocket. Two minutes later, he emerges. The camera offers an unflattering close-up of his bald spot.

Facebook Twitter Pinterest Lugovoi walking up the stairs from the Millennium hotel foyer. The image is striking. ‘Lugovoi seems preoccupied. He’s unusually pale, grim, grey visaged. His left hand is concealed in a jacket pocket.’

Then, at 3.45pm, Kovtun repeats the same procedure, asking for directions, vanishing into the men’s toilets, reappearing three minutes later. He is a slight figure. What were the pair doing there? Washing their hands, having set the polonium trap? Or preparing the crime, a heinous one, in the sanctuary of one of the cubicles?

Tests were to show massive alpha radiation contamination in the second cubicle on the left – 2,600 counts per second on the door, 200 on the flush handle. Further sources of polonium were found on and below the gents’ hand-dryer, at over 5,000 counts per second. There was what scientists called “full-scale deflection” – readings so high they were off the scale.

Facebook Twitter Pinterest Dmitry Kovtun arrives at the Millennium. Photograph: Litvinenko Inquiry/PA Wire

The multiplex system shows someone else arriving at 15.59 and 41 seconds – a fit-looking individual, wearing a blue denim jacket with a fawn collar. He is on his mobile phone. This is Litvinenko at the blurred edge of the picture; he calls Lugovoi from the hotel lobby to tell him that he has arrived. The CCTV tells us little beyond this. Apart from one important detail. Litvinenko never visits the hotel bathroom. He is not the source of the polonium; it is his Russian companions-turned-executioners who bring it with them to London, in this, their second poisoning attempt.

* * *

The Soviet Union had a long tradition of bumping off its enemies. They included Leon Trotsky (ice-pick in the head), Ukrainian nationalists (poisons, exploding cakes) and the Bulgarian dissident Georgi Markov (ricin pellet fired from an umbrella, on London’s Waterloo Bridge). There was a spectrum. It went from killings that were demonstrative, to those where the KGB’s fingerprints were nowhere to be found, however hard you looked. Such murders were justified by what you might call Leninist ethics: they were necessary to defend the Bolshevik revolution, a noble experiment.

Facebook Twitter Pinterest Litvinenko arrives at the Millennium hotel.

Under Boris Yeltsin these exotic killings mostly stopped. Moscow’s secret poisons lab, set up by Lenin in 1917, was mothballed. After 2000 though, with Putin in the Kremlin, such Soviet-style operations quietly resumed. Critics of Russia’s new president had an uncanny habit of ending up ... well, dead. In power, Putin steered the country in an increasingly authoritarian direction, snuffing out most sources of opposition and dissent. The president’s fellow KGB comrades, once subordinate to the Communist party, were now in sole charge.

The murders of journalists and human rights activists could not be explained in terms of protecting socialism. Rather, the state was now synonymous with something else: the personal financial interests of Putin and his friends.

As an FSB officer in the 1990s, Litvinenko had been shocked to discover how thoroughly organised crime had penetrated Russia’s security organs. In his view, criminal ideology had replaced communist ideology. He was the first to describe Putin’s Russia as a mafia state, in which the roles of government, organised crime and the spy agencies had grown indistinguishable.

While serving with the FSB, where his role was akin to that of a detective, Litvinenko had also perfected his observation skills. It was part of his basic training. How to describe the bad guys: their height, build, hair colour and distinguishing features. What they were wearing. Any jewellery. How old. Smoker or non-smoker. And of course their conversation – from the major stuff, such as admissions of guilt, down to trivial details. For example, who offered whom a cup of tea?

When DI Brent Hyatt of Scotland Yard later interviewed Litvinenko, the Russian gave him a full and – in the circumstances, remarkable – account of his meeting with Lugovoi and Kovtun in the Pine Bar. Litvinenko said that Lugovoi approached him in the foyer from the left side and said: “Let’s go, we are sitting there.” He followed Lugovoi into the bar; Lugovoi had already ordered drinks. Lugovoi sat with his back to the wall; Litvinenko was diagonally across from him on a chair. There were glasses on the table – but no bottles. And “mugs and a teapot”.

As Lugovoi knew, Litvinenko did not drink alcohol. Moreover he was hard-up and reluctant to spend any money of his own in a fancy establishment. The barman, Norberto Andrade, approached Litvinenko from behind, and asked him: “Are you going to have anything?” Lugovoi repeated the question and said: “Would you like anything?”. Litvinenko said he did not want anything.

Litvinenko told Hyatt: “He [Lugovoi] said, ‘OK, well we’re going to leave now anyway, so there is still some tea left here, if you want to you can have some.’ And then the waiter went away, or I think Andrei asked for a clean cup and he brought it. He left and when there was a cup, I poured some tea out of the teapot, although there was only a little left in the bottom and it made just half a cup. Maybe about 50 grammes.

“I swallowed several times but it was a green tea with no sugar and it was already cold, by the way. I didn’t like it for some reason, well, almost cold tea with no sugar, and I didn’t drink it any more. Maybe in total I swallowed three or four times.” Litvinenko said he didn’t finish the cup.

Hyatt: The pot with the tea in it was already there?

Litvinenko: Yes.

Hyatt: How many mugs were on the table when you came in?

Litvinenko: I think three or four cups.

Hyatt: And did Andrei drink any more from the pot in your presence?

Litvinenko: No.

Hyatt: OK, and what happened next?

Litvinenko: Then he said Vadim [Kovtun] is coming here now ... either Vadim or Volodia, I can’t remember. I saw him for the second time in my life.

Hyatt: What happened next?

Litvinenko: Next Volodia [Kovtun] took a place at the table on my side, across from Andrei.

The three men discussed their meeting scheduled for the following day at the private security firm Global Risk. In previous months, Litvinenko had tried to supplement his £2,000-a-month MI6 salary by doing due diligence reports for British firms keen to invest in Russia. The bar was crowded, Litvinenko said. He felt a strong antipathy towards Kovtun. It was only their second encounter. There was something strange about him, Litvinenko thought – as if he were in the midst of some personal torment.

Litvinenko: Volodia [Kovtun] was – seemed to be – very depressed, as if he was very much hungover. He apologised. He said that he hadn’t slept for the whole night, that he had just flown in from Hamburg and he wanted to sleep very much and he couldn’t stand it any more. But I think he is either an alcoholic or a drug addict. He is a very unpleasant type.

Hyatt: Volodia, how did he know to come to the table? Did Andrei contact him and ask him to come and join you, or was there already an arrangement for him to join you?”

Litvinenko: No … he [Kovtun], I think he knew in advance. Even possibly they had been sitting before this and maybe he went up to his room.

Hyatt: Just going back to when you had some tea, you didn’t ask the waiter for a drink. It was mentioned that there was some tea left. How insistent was Andrei that you have a drink, or was he indifferent? Was he saying, “Go on, go on, have some?” Or didn’t he care?

Litvinenko: He said it like that, you know, “If you would like something, order something for yourself, but we’re going to be leaving soon. If, if you want some tea, then there is some left here, you can have some of this...”

I could have ordered a drink myself, but he kind of presented in such a way that it’s not really need to order. I don’t like when people pay for me but in such an expensive hotel, forgive me, I don’t have enough money to pay for that.”

Hyatt: Did you drink any of the tea in the presence of Volodia?

Litvinenko: No, I drank the tea only when Andrei was sitting opposite me. In Volodia’s presence, I wasn’t drinking it .... I didn’t like that tea.

Hyatt: And after you drank from that pot, did Andrei or Volodia drink anything from that pot?

Litvinenko: No, definitely. Later on, when I left the hotel, I was thinking there was something strange. I had been feeling all the time, I knew that they wanted to kill me.

There is no evidence to say whether it was Kovtun – an ex‑waiter, who once worked in a Hamburg restaurant – or Lugovoi who put polonium in the teapot. From Litvinenko’s testimony, it is clear that this was a joint criminal enterprise. Lugovoi would subsequently explain that he could not recall what drinks he had ordered in the Pine Bar. And that Litvinenko had insisted upon their meeting, to which he had reluctantly assented.

Subsequently, police tracked down Lugovoi’s bar bill. The order was: three teas, three Gordon’s gin, three tonics, one champagne cocktail, one Romeo y Julieta cigar No 1, one Gordon’s gin. The tea came to £11.25; the total bill £70.60. Lugovoi was a man who murdered with a certain breezy style.

By this point, Lugovoi and Kovtun must have concluded that their poisoning operation had worked. Litvinenko had drunk the green tea. Not much, admittedly. But, he had drunk. Surely, enough? The meeting lasted 20 minutes. Lugovoi gazed at his watch. He said he was expecting his wife. She appeared in the foyer and, as if on cue, waved her hand, and mouthed: “Let’s go, let’s go.” Lugovoi got up to greet her, and left Litvinenko and Kovtun sitting together at the table.

There was one final, scarcely believable scene. According to Litvinenko, Lugovoi came back to the bar accompanied by his eight-year-old son Igor. Lugovoi introduced him to Litvinenko. He said to Igor: “This is Uncle Sasha, shake his hand.”

Igor was a good boy. He obediently shook Litvinenko’s hand, the same hand that by now was pulsing with radiation. When police examined Litvinenko’s jacket they found massive contamination on the sleeve – Litvinenko had picked up and drunk the tea with his right hand. The party, plus Litvinenko, left the bar. The Lugovoi family and Sokolenko went off to the match. Kovtun declined to go, declaring: “I’m very tired, I want to sleep.”

Igor was a good boy. He obediently shook Litvinenko’s hand, the same hand that by now was pulsing with radiation

Forensic experts would test the entire bar area, the tables, and crockery. They examined 100 teapots, as well as cups, spoons, saucers, milk jugs. Litvinenko’s white ceramic teapot was not difficult to discover – it gave off readings of 100,000 becquerels per centimetre squared. The biggest reading came from the spout. (The teapot was put in the dishwasher afterwards and unknowingly reused for subsequent customers.) The table where they sat registered 20,000 becquerels. Half that, ingested, was enough to kill a person.

Facebook Twitter Pinterest Lugovoi and Kovtun at a press conference in Moscow, in 2006. Photograph: Alexander Zemlianichenko/AP

Polonium was a miasma, a creeping fog. It was found inside the dishwasher, on the floor, till, a coffee strainer handle. There were traces on bottles of Martini and Tia Maria behind the bar, the ice-cream scoop, a chopping board. It turned up on chairs – with large alpha radiation readings from where the three Russians sat – and the piano stool. Whoever sent Lugovoi and Kovtun to London must have known of the risks to others. Apparently they didn’t care.

The most crucial piece of evidence was discovered several floors above the Pine Bar, in Kovtun’s room, 382. When police forensic teams took apart the bathroom sink they found a mangled clump of debris. The debris was stuck in the sediment trap of the sink’s waste pipe. Tests on the clump showed it contained 390,000 becquerels of polonium. The levels were so high that they could only have come from polonium itself.

After laying the poison in Litvinenko’s teapot, Kovtun had gone back upstairs to his room. There, in the privacy of the bathroom, he had tipped the rest of the liquid solution down the sink. No one else – other than Lugovoi and Sokolenko – had access to the room. Police concluded that Kovtun had knowingly handled the murder weapon, and afterwards got rid of it. It was an intentional act of disposal.

The science was objective, conclusive and utterly damning. It had the simplicity of undeniable fact. Back in Moscow, in numerous subsequent interviews, Kovtun would claim innocence. He was never able to explain away this piece of evidence: why was the polonium in his bathroom?

Polonium was a miasma, a creeping fog. It was found inside the dishwasher, on the floor, till, a coffee strainer handle

The Russian operation to murder Litvinenko would have had a codename -– thus far unknown. It could finally be marked down as a success. It was the sixth anniversary of Litvinenko’s arrival in Britain: 1 November 2000. He did not know it yet, but he was dying. The substance used to kill him had been chosen because the killers believed it could not be detected. The plan was working. From this point on nothing – not even the most gifted medical team from the heavens – could save him.

* * *

Seventeen days later, Litvinenko was lying in hospital, mortally ill. His case had baffled medical staff. Eventually, they had alighted on a diagnosis of thallium poisoning. This late stage saw the arrival of Scotland Yard.

To begin with, the British police had a confusing picture – a poisoned Russian who spoke poor English; a baffling plot involving visitors from Moscow; and a swirl of potential crime scenes. Two detectives, DI Brent Hyatt and DS Chris Hoar, from the Met’s specialist crime unit, interviewed Litvinenko in the critical care unit on the 16th floor of University College Hospital. He had been admitted as Edwin Redwald Carter, his British pseudonym. He is a “significant witness” in the investigation. There are 18 interviews, lasting eight hours and 57 minutes in total. These conversations stretch out over three days, from the early hours of 18 November until shortly before 9pm on 20 November.

The interview transcripts were kept secret for eight-and-a-half years, hidden in Scotland Yard’s case file, and stamped with the word “Restricted”. Revealed in 2015, they are remarkable documents. They are, in effect, unique witness statements taken from a ghost. But Litvinenko is no ordinary ghost: he is a ghost who uses his final reserves of energy to solve a chilling murder mystery – his own.

Litvinenko was a highly experienced detective. He knew how investigations worked. He was fastidious too: neatly collating case materials in a file, always employing a hole‑punch. In the interviews, he sets out before the police in dispassionate terms the evidence of who might have poisoned him. He acknowledges: “I cannot blame these people directly because I have no proof.”

He is an ideal witness – good with descriptions, heights, details. He draws up a list of suspects. There are three of them: the Italian Mario Scaramella; his business partner Andrei Lugovoi, and Lugovoi’s unpleasant Russian companion, whose name Litvinenko struggles to remember, and to whom he refers wrongly as “Volodia” or “Vadim”.

Hyatt begins recording at eight minutes after midnight on 18 November. He introduces himself and his colleague DS Hoar. Litvinenko gives his own name and address.

Hoar then says: “Thank you very much for that, Edwin. Edwin, we’re here investigating an allegation that somebody has poisoned you in an attempt to kill you.” Hoar says that doctors have told him Edwin is suffering from “extremely high levels of thallium” and “that is the cause of this illness”.

He continues: “Can I ask you to tell us what you think has happened to you and why?”

Medical staff had pre-briefed Hoar that Litvinenko spoke good English. Hoar discovered that was not true. After this first conversation, an interpreter was brought in.

Litvinenko is still able to give a full account of his career in the FSB, his deepening conflict with the agency. He also talks of his “good relationship” with the Russian journalist Anna Politkovskaya, another Putin enemy, and her fear that she was in danger. In spring 2006, they met in a branch of Cafe Nero in London. Litvinenko asked her what was wrong. She told him: “Alexander, I’m very afraid,” and said that every time she said goodbye to her daughter and son she had the feeling she was looking at them “for the last time”. He urged her to leave Russia. She said she could not – her parents were old, she had kids. In October 2006, Politkovskaya was shot dead in the stairwell of her Moscow apartment.

Politkovskaya’s murder left Litvinenko “very, very shocked”, he says, adding: “I lost of a lot of my friends”, and that human life in Russia is cheap He tells detectives about his speech in the Frontline Club, a press club in London, the previous month, in which he accused Putin publicly of having Politkovskaya killed.

From time to time, the interviews stop: the tape runs out; nurses come in to administer drugs; Litvinenko, suffering from diarrhoea, has to go to the bathroom. Mostly, though, he battles on. He tells Hyatt: “Meeting you is very important for my case.”

Facebook Twitter Pinterest The journalist Anna Politkovskaya, a friend of Litvinenko, was shot dead in 2006.

Photograph: Fyodor Savintsev/AP

It is the two Russians who are at the centre of his suspicions. Litvinenko recounts his meeting with them at the Millennium. He says that he had not been to the hotel before and that he had to find it on a map. He insists this “special” information remain secret – not to be made public or shared with his wife Marina. “These people, it’s interesting. Most interesting,” he muses.

With time running out, Litvinenko is working furiously to solve the conundrum. The transcript reads:

Carter [Litvinenko]: Only these three people can poison me.

Hyatt: These three.

Carter: Mario, Vadim [Kovtun] and Andrei.

There are moments when it appears that there are three officers hard at work: Hyatt, Hoar and Litvinenko, the punctilious ex-cop. After four or five hours of interviews, the case begins to cohere. The investigation gains new momentum. Information is passed back to SO15, the counter-terrorist command at Scotland Yard, headed by Det Supt Clive Timmons.

Litvinenko explains that his most important papers are kept at home, in the lower shelf of a large cupboard. The papers include critical information on Putin, and the people around him, from newspapers and other sources, as well as background on Russian criminal gangs. He gives the police his email password and bank account. He tells them where they can find receipts for two Orange sim cards, bought for £20 from a store in Bond Street – in a black leather wallet on his bedside table. Litvinenko explains that he gave one of the sims to Lugovoi; they used these secret numbers to communicate. He hands over his diary.

Ever helpful, Litvinenko phones his wife and asks her to locate a photo of Lugovoi at their home. Hyatt suspends the interview to secure the photograph. Lugovoi is now a prime suspect. Litvinenko describes him like this: “Andrei is a pure European, and even he looks a little bit like me, sort of. The same type as like me ... I am 1m 77cm – 1m 78cm, so he is probably 1m 76cm. He is two years younger than me, light hair.” He has a small, “almost invisible” bald patch.

The transcript reads:

Hyatt: Edwin, do you consider Andrei to be a friend of yours, or a business associate? What, how do you describe your relationship with Andrei?

Carter: ... He is not a friend. He is a business partner.

At the end of his second day of interviews, on 19 November, Litvinenko describes getting a lift home with a Chechen friend named Akhmed Zakayev: “Now the paradoxical thing is that I was still feeling very well but then somehow I had some kind of feeling that something might happen to me in the nearest future. Maybe subconsciously.” The detectives turn off the tape. It is a full and frank account of events leading up to Litvinenko’s poisoning – with one exception. During these two days he does not mention his secret life and his job working for British intelligence. It is only the next day that he speaks of his meeting on 31 October with his MI6 handler “Martin”, in the basement cafe of the Waterstone’s bookshop on Piccadilly. Litvinenko is chary – evidently reluctant to discuss his undercover role.

Carter: On 31 October at about 4pm, I had a meeting arranged with a person about whom I wouldn’t really like to talk here because I have some commitments. You can contact that person on that long telephone number which I gave you.

Hyatt: Did you meet with that person, Edwin?

Carter: Yes.

Hyatt: Edwin, it could be absolutely vital that you tell us who that person is.

Carter: You can call him and he will tell you.

The interview abruptly stops. It’s 5.16pm. Hyatt dials the long telephone number, reaches “Martin”, and tells him that Litvinenko is gravely ill in hospital, the victim of an apparent poisoning by two mysterious Russians.

Facebook Twitter Pinterest Police investigate Litvinenko’s poisoning at the Millennium hotel in central London. Photograph: Alessia Pierdomenico/Reuters

It appears to be the first time that MI6 – an organisation famed for its professionalism – learns of Litvinenko’s plight. Litvinenko, of course, was not a full-time employee. But he was a salaried informant, with his own encrypted mobile phone and MI6-provided passport. The agency appears not to have classified Litvinenko as being at risk, despite numerous threatening phone calls from Moscow and a firebomb attack on his north London home in 2004.

MI6’s reaction is unclear. The British government has still refused to release the relevant files. One can imagine panic and embarrassment. And the agency shifting into full-blown crisis mode. The transcripts show that after speaking to DI Hyatt, “Martin” scrambled to Litvinenko’s hospital bedside. He talked to his poisoned agent, and left around 7.15pm. The police interview then resumes; the final exchanges deal with earlier threats against Litvinenko from the Kremlin and its emissaries. The detectives ask if there is anything Litvinenko would like to add:

Hoar: Can you think of anybody else who may wish to do this sort of harm to you?

Carter: I have no doubt who wanted it, and I often receive threats from these people. This was done … I have no doubt whatsoever that this was done by the Russian Secret Services. Having knowledge of the system I know that the order about such a killing of a citizen of another country on its territory, especially if it is something to do with Great Britain, could have been given by only one person.

Hyatt: Would you like to tell us who that person is, sir? Edwin?

Carter: That person is the president of the Russian Federation, Vladimir Putin. And if ... you of course know, while he’s still president, you won’t be able to prosecute him as the main person who gave that order, because he is the president of a huge country crammed with nuclear, chemical and bacteriological weapons. But I have no doubt whatsoever that as soon as the power changes in Russia or when the first officer of Russian Special Services defects to the west he will say the same. He will say that I have been poisoned by the Russian Special Services on Putin’s order.

* * *

Litvinenko’s condition was rapidly deteriorating. On 20 November, the same day as his last police interview, doctors moved him to intensive care. There it was easier to monitor him and, if necessary, to intervene. Litvinenko’s heart rate was becoming abnormal; his major organs failing.

The medics treating him were in uncharted territory. Litvinenko’s case was problematic: his symptoms were not consistent with thallium poisoning. He had severe bone marrow failure and gut damage, which fitted. But he lacked one key symptom of thallium poisoning – peripheral neuropathy, pain or numbness in his fingers and feet. “It was still a bit of a mystery,” one doctor said.

Meanwhile, those close to Litvinenko were reluctantly concluding that he was unlikely to survive.

The Kremlin would subsequently accuse Litvinenko’s friend Alex Goldfarb, and Boris Berezovsky of cynically exploiting him, as part of their long-running public relations campaign against Putin. In fact, Litvinenko made it abundantly clear – as the Scotland Yard transcripts show – that he held Putin personally responsible for his poisoning. And he wanted to send this message to the world.

Litvinenko’s lawyer, George Menzies, began drafting a statement on his behalf. Menzies later said that the ideas in it were wholly Litvinenko’s. “I was doing my best, in personal terms, to represent what I truly believed to be Sasha’s state of mind and sentiment,” he said. Its themes – Litvinenko’s pride in being British, his love of his wife, his belief as to the source of his illness – mirrored what his client thought, Menzies said.

Goldfarb and Menzies took the draft to the hospital. They showed it to Marina. Her reaction was negative. She believed her husband would pull through and that writing a last testament was tantamount to giving up on him. Pragmatically, they told her: “Better to do it now than later.”

Menzies consulted with Tim Bell, chairman of the London PR firm Bell Pottinger. Bell’s company had worked for Berezovsky since 2002, helping the exiled oligarch through various legal scrapes, and had assisted the Litvinenkos as well. Bell said he thought the text was too gloomy and read like a “deathbed statement.” “I didn’t think it was the right thing to do because I still hoped and believed Sasha would live,” Bell said.

Goldfarb read out the A4 sheet to Litvinenko in intensive care, translating it from English to Russian. At one point Goldfarb made a movement with his arms, mimicking the flight of an angel flapping its wings. Litvinenko endorsed the statement in its entirety, confirming: “This is exactly what I want to say.” Litvinenko then signed and dated it – 21 November 2006, his signature trailing off into a black swirl.

The statement accused Litvinenko’s one-time FSB boss of murder, and ended: “You may succeed in silencing one man but the howl of protest from around the world will reverberate, Mr Putin, in your ears for the rest of your life.”

TV cameras and media had gathered outside the hospital’s main gate, waiting for news.

Sixteen floors above them, Litvinenko asked Goldfarb if he was a big story. He was – but not much was known about Litvinenko, other than that he was a prominent critic of Putin’s, and desperately ill. Goldfarb said: “Sasha, if you really want the message to be seriously put across, we need a photo.” Marina was against the idea, and saw it as an invasion of privacy. But Litvinenko agreed, and said: “Yes, if you think it’s needed, let’s do it.”

Goldfarb rang Bell Pottinger and spoke to Jennifer Morgan, Bell’s liaison. Morgan in turn called a photographer she knew, Natasja Weitsz. Weitsz arrived at the hospital and was escorted upstairs past a police guard. She was with Litvinenko for mere minutes. He pushed his green hospital gown to one side so as to reveal the electro-cardiagram sensors attached to his heart. Weitsz shot a couple of frames of Litvinenko: bald, gaunt and defiant, staring with cornflower-blue eyes directly at the camera lens. The image was cropped around its haunting subject. It went round the world.

Facebook Twitter Pinterest Marina Litvinenko in 2012. Photograph: Oli Scarff/Getty Images

By the next day, Wednesday 22 November, doctors treating Litvinenko had scrapped their diagnosis. Their notes read: “We DO NOT feel this gentleman has or had inorganic thallium poisoning.”

At midday, a top-level meeting was convened at the Met’s counter-terrorism command. It involved SO15 detectives, led by Det Supt Timmons, medical staff, a scientist from the UK’s atomic weapons establishment, the forensic science service and Dr Nick Gent from Porton Down, the UK’s military science facility. The latest urine test had revealed the presence of a new radioactive isotope – polonium-210. But this was marked down as an anomaly, caused by the plastic container used to carry the sample.

According to Timmons, the specialists discussed five theories that might explain Litvinenko’s baffling poisoning. Most were esoteric. The experts decided to investigate further and to send a litre of urine to Aldermaston.

Back in the intensive care ward, Litvinenko was drifting in and out of consciousness. The Russian-German film-maker Andrei Nekrasov visited him. Nekrasov had previously conducted several interviews with Litvinenko; he shot the video on condition that it would be released only with Marina’s approval. Litvinenko lies on his bed, a vanquished soul, around whom the world is darkening. A drip is attached to his nose; his cheeks are hollow; his eyes are open – just. There is pale afternoon light.

“He was conscious, but was very, very weak,” Marina said. “I spent almost all day sitting close to him, [to] make him just be calm and more relaxed.” At 8pm Marina got up to leave, and told her husband: “Sasha, unfortunately I have to go.”

She said: “He smiled so sadly, and I started to feel I’m guilty because I’m leaving him, and I just said: ‘Don’t worry, tomorrow morning I will come and everything will be fine.’”

Litvinenko whispered back to her: “I love you so much.”

At midnight the hospital called to say that Litvinenko had gone into cardiac arrest, not once but twice. The medics managed to resuscitate him. Marina returned to University College Hospital, getting a lift with Zakayev, and found her husband unconscious and on a life-support machine. She spent the following day, 23 November, at his side; Litvinenko was in an induced coma. That evening she went back to Muswell Hill. An hour after arriving home the phone rang. It was the hospital telling her urgently to return.

Litvinenko suffered a third cardiac arrest at 8.51pm. The consultant on duty, Dr James Down, tried to revive him but at 9.21pm pronounced him dead. When Marina and Anatoly arrived at the hospital they were taken not to the ward but to a side room. Ten or 15 minutes later, the doctor told them that Litvinenko had died. He added: “Would you like to see Sasha?” to which Marina replied: “Of course.”

For the first time in several days, Marina was allowed to touch and kiss her husband; Anatoly ran from the room after half a minute.

Six hours before Litvinenko’s death, at about 3pm, Timmons received a phone call from the atomic weapons establishment. It had the results from the latest tests. They confirmed that Litvinenko was “terribly contaminated”, as Timmons put it, with radioactive polonium.

• A Very Expensive Poison by Luke Harding will be published in March by Guardian Faber (£12.99). To order a copy for £7.99, go to bookshop.theguardian.com or call 0330 333 6846. Luke Harding will be in conversation with Marina Litvinenko at a Guardian Live event on Thursday 17 March. Tickets £10. His previous non-fiction books include Mafia State and The Snowden Files.

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