Two Russian businessmen, Andrey Lugovoi and Dmintry Kovtun, arrive in London. The trail of radioactive Polonium -210 (Po-210) discovered later by the police starts on that day in Mr. Lugovoi's hotel room.

In the afternoon Lugovoi and Kovtun meet Alexander Litvinenko at a Sushi bar on Picadilly. The bar gets heavily contaminated by Po-210, but Litvinenko remains unharmed.

October 18, 2006

Lugovoi and Kovtun leave for Moscow contaminating the planes with Po-210

October 30, 2006

Lugovoi and Kovtun return to London via separate routes, Lugovoi on a direct flight from Moscow, and Kovtun, via Hamburg, where he visits his family. The planes they took are contaminated by Po-210

October 31, 2006

Lugovoi visits Boris Berezovsky at his Mayfair office. He leaves a trace of Po-210 on the sofa.

1 November 2006

Litvinenko meets Lugovoi and Kovtun at the Pine Bar in the Millennium Hotel in Mayfair, and is poisoned with Po-210 placed in a cup of tea. Later he starts to feel unwell, his condition worsens into the night.

Lugovoi and Kovtun return to Moscow

4 November 2006

Litvinenko is admitted to Barnett hospital.

17 November 2006

Litvinenko's condition worsens and he is transferred to University College Hospital under police guard. Counter terrorist division of Scotland Yard begins investigating the case.

19 November 2006

Doctors suspect that Litvinenko has been poisoned with thallium.

20 November 2006

Litvinenko is moved to intensive care and pictures showing his failing health are released.

21 November 2006

Doctors rule out thallium as the cause of Litvinenko's illness. Toxicologist John Henry says the symptoms resemble radiological damage. But no traces of radioactivity is found.

22 November 2006

Litvinenko's condition is described as critical. He suffers a heart attack overnight.

23 November 2006

Litvinenko dies.

24 November 2006

In the early hours radiological analysis concludes that Litvinenko died from radiation poisoning caused by Po-210, a rare isotope undetectable with common hospital equipment. At 3 am Scotland Yard evacuates Marina Litvinenko and her son Anatoly from their home.

Litvinenko's friend Alex Goldfarb reads to the press his deathbend statement accusing Vladmir Putin of his murder: “Protest from around the world will reverberate, Mr Putin, in your ears for the rest of your life”.

At a press conference in Helsinki Vldimir Putin says: “Litvinenko's death is, of course, a tragedy, but there is no evidence that it is of a violent nature”.

28 November 2006

Thousands of people call NHS Direct over the radition alert.

Tony Blair says no "diplomatic or political barrier will stand in the way of the police investigation”.

29 November 2006

Two British Airways Boeing 767s are grounded at Heathrow after traces of radioactivity are found. BA begins contacting thousands of passengers who travelled on board.

Hospital staff is assessed for exposure.

30 November 2006

Home Secretary John Reid announces that traces of radioactivity had been discovered in 12 locations in London.

An inquest into Litvinenko’s death is opened and adjourned.

1 December 2006

Marina Litvinenko tests positive for Polonium-210.

4 December 2006

The police find traces of Polonium at the Parkes Hotel in Knightsbridge the Best Western Hotel on Shaftesbury Avenue, where Lugovoi and Kovtun stayed on October 16.

7 December 2006

Litvinenko is buried at Highgate Cemetery. To avoid contamination of the environment he is buried in a sealed coffin.

9 December 2006

German police find traces of radiation in the Hamburg flat of Mr Kovtun's ex wife and her mother's home.

10 December 2006

Marina Litvinenko tells the Mail on Sunday that she believes the Russian Government could be behind her husband's murder.

Kovtun's ex-wife and two children test positive for radiation.

British and Russian authorities interview Andrei Lugovoi in Moscow.

11 January 2007

Of the 596 people tested 120 had shown evidence of exposure, 13 of those are believed to be at risk of health implications.

The HPA says 450 people have been identified at risk internationally in 48 countries.

22 January 2007

BBC 'Panorama' reports that the poisoning on November 1 may have the second attempt on Litvinenko's life; the first may have happened on 16 October at the Itsu sushi bar.

Marina Litvinenko tells BBC that the murder could not have been carried out without President Putin's knowledge. Mr Putin's office denies the allegation and accuses Marina of lying.

31 January 2007

The Police investigation is concluded and the file is handed to the Crown Prosecution Service. BBC, citing police sources, reports that former KGB officer Andrey Lugovoi is a suspect.

28 May 2007

The British Foreign Office submits a formal request to the Russian Government for the extradition of Andrei Lugovoi to the UK to face criminal charges relating to Litvinenko's murder

31 May 2007

Lugovoi holds a news conference, at which he accused MI6 of attempting to recruit him and blamed either MI6, the Russian mafia, or Boris Berezovsky for the killing.

July 5, 2007

Russia formally rejects a British request to extradite the suspect citing constitutional prohibition of extradition of citizens.

16 July 2007

The British Foreign Office confirms that four Russian diplomats are to be expelled from the Russian Embassy in London. Britain suspends security cooperation with Russia and introduces visa restrictions for certain categories of Russian officials.

19 July 2007

Russia expells four UK diplomats from the British Embassy in Moscow

Summer 2007

The book Death of a Dissident: The Poisoning of Alexander Litvinenko and the Return of the KGB by Alex Goldfarb and Marina Litvinenko is released in different countries.

March 27, 2008

In an article in Sunday Times Marina Litvinenko says that she will press for a full inquest into the death of her husband against the wishes of the Foreign office.

April 1, 2008

The US House of representatives passes a resolution expressing concerns that “elements of the Russian government” are behind Litvinenko murder.

July 7, 2008

A British secret service source tells the BBC's Newsnight: "We very strongly believe the Litvinenko case to have had some state involvement."

September 11, 2011

British PM David Cameron travels to Moscow to see Putin, in a first British official contact with him since Litvinenko's death. Russian president Dmitry Medvedev tells Cameron that Lygovoi "will never be extradited".

September 25, 2011

Putin announces that he will run for presidency in the 2012 election.

October 1, 2011

Marina Litvinenko anounced that she will present her arguments for a full inquest at Coroner's hearing on October 13. It is revealed that Lugovoi will be represented by a British lawyer