The hunt for the truth behind the mysterious illness that killed former Russian spy Alexander Litvinenko became a dark political drama worthy of a film plot.

Here is a timeline of events:

 

OCTOBER 7, 2006 Journalist Anna Politkovskaya, a prominent critic of the war in Chechnya, is found dead in her apartment building in Moscow with two gunshot wounds, one to the head.

Colleagues said she had frequently received threats and was targeted for her outspoken views. In Britain, former Russian spy Alexander Litvinenko, another outspoken critic of the Kremlin, begins to investigate the murder.

 

NOVEMBER 1 Mr Litvinenko meets two Russian men at a London hotel - one a former KGB officer. It is not clear what is discussed at the meeting.

Later, he meets Italian academic Mario Scaramella at a sushi bar in Piccadilly where it is said he receives documents claiming to name Ms Politkovskaya's killers.

Several hours after the meeting Mr Litvinenko complains of feeling sick and he is admitted to Barnet General Hospital in north London.

 

NOVEMBER 11 Mr Litvinenko gives an interview to the BBC's Russian Service where he describes being in "very bad shape" following a "serious poisoning". Commenting on the meeting with Mr Scaramella at the sushi bar, he says: "He passed me some papers, where the person was named, who apparently might be connected to the murder of Anna Politkovskaya.

"That's it. After several hours I felt sick with symptoms of poisoning."

 

NOVEMBER 17 Mr Litvinenko is transferred to University College Hospital in central London as his condition deteriorates. He is placed under armed guard.

 

NOVEMBER 19Reports emerge in the British press that Mr Litvinenko has been poisoned with thallium, a highly toxic, colourless and odourless chemical once used in rat and ant killer.

Alex Goldfarb, a friend of Mr Litvinenko who helped bring him to Britain six years ago, says he looks "like a ghost" in hospital. He reveals that Mr Litvinenko has lost all his hair, has to be fed intravenously, and is very weak.

Friends of Mr Litvinenko say doctors have only given him a 50/50 chance of surviving the next few weeks.

 

NOVEMBER 20 University College Hospital says Mr Litvinenko has been moved to intensive care after a "slight deterioration" in his condition overnight.

Later in the day, dramatic pictures of the former Russian security agent are released, graphically illustrating how his physical appearance has been affected.

Scotland Yard says its counter terrorism unit is investigating the cause of Mr Litvinenko's illness. It says detectives are treating the case as a suspected "deliberate poisoning" but are awaiting the results of toxicology tests. Officers have already spoken to Mr Litvinenko, and hope to interview him again when he is well enough, police add.

Meanwhile, a senior Kremlin spokesman dismisses allegations that Russia's government was involved in the poisoning as "sheer nonsense".

 

NOVEMBER 21 John Henry, a toxicologist involved with the treatment of Mr Litvinenko, says he may have been poisoned with "radioactive thallium".

He says the damage to Mr Litvinenko's bone marrow and his blood cells suggests a radioactive element to the poisoning.

Doctors directly responsible for his treatment later say Mr Litvinenko's illness is unlikely to have been caused by ordinary thallium poisoning.

Meanwhile, Mr Scaramella claims Mr Litvinenko saw documents naming him as a target during their meeting on November 1.

 

NOVEMBER 22 University College Hospital says Mr Litvinenko's condition has deteriorated slightly from the day before, while friends also say he looks worse. Meanwhile, Russia's foreign intelligence service denies involvement in the poisoning of Mr Litvinenko.

"Litvinenko is not the kind of person for whose sake we would spoil bilateral relations," Sergei Ivanov, a spokesman for the Foreign Intelligence Service, is quoted as saying.

 

NOVEMBER 23 Mr Litvinenko dies in University College Hospital at 9.21pm. Overnight he suffered a heart attack and his condition deteriorated dramatically.

Doctors and police were still unsure what made him ill, having ruled out speculation that the heavy metal thallium was to blame for his sickness and also said radiation poisoning was unlikely.

The matter is now an investigation being dealt with by detectives from New Scotland Yard.

 

NOVEMBER 24 A statement dictated by Mr Litvinenko on November 21 is read in which he says to the "person responsible" for his poisoning "you have shown yourself to be as barbaric and ruthless as your most hostile critics have claimed".

Home Secretary John Reid says police investigating the death have called in expert assistance to search for any traces of radioactive material at a number of locations.

The announcement comes 24 hours after doctors treating Mr Litvinenko said radiation poisoning was "unlikely".

The Health Protection Agency (HPA) says Mr Litvinenko had "apparently been poisoned by a type of radiation", and tests had established that he had a "significant quantity" of the radioactive isotope polonium-210 in his urine.

The HPA confirms that traces of radiation have been found at the sushi bar and at the London hotel visited by Mr Litvinenko.

 

NOVEMBER 26 It emerges that counter-terrorist detectives are now treating Mr Litvinenko's death as suspicious after days of simply saying it was "unexplained".

 

NOVEMBER 27 Home Secretary John Reid says the Russian authorities have been asked to provide "all necessary co-operation" with the investigation into the death of Mr Litvinenko.

Scotland Yard says traces of polonium 210 have been found at offices at 7 Down Street and 25 Grosvenor Street in London.

The Grosvenor Street address houses the headquarters of international security company Erinys, visited by Mr Litvinenko.

Mr Goldfarb confirms that the address in Down Street was the office of exiled billionaire Boris Berezovsky, a friend of Mr Litvinenko.

 

NOVEMBER 28 It emerges that eight people are being tested for possible contamination following Mr Litvinenko's death.

Police investigating the poisoning extend their search to the five-star Sheraton Park Lane Hotel in London as well as an office building at 58 Grosvenor Street.

 

NOVEMBER 29Up to 33,000 passengers and 3,000 British Airways staff are caught up in the investigation after the airline said that "low levels of radioactive traces" had been found on two of its aircraft at Heathrow airport.

Experts were preparing to examine a third aircraft in Moscow, it added.

The alert involved 221 flights within Europe made by the three short haul 767s.

 

[Later Reports: The radiation was traced to a nuclear plant in Russia, and the Kremlin continued to deny involvement].