Who was Alexander Litvinenko?
A pre-inquest review over the death of Alexander Litvinenko has taken place. But who was he and why did his death become such a cause celebre?
Before he was poisoned and died in November 2006, few outside Russia had ever heard of Alexander Litvinenko.
A 43-year-old former officer with the Federal Security Service (FSB), Mr Litvinenko had become a useful, if not entirely reliable, source for journalists interested in the machinations of Vladimir Putin's Russia.
But it has since emerged the Russian spy was being paid by both the British secret service MI6 and the Spanish secret service.
He was allegedly investigating Spanish links to the Russian mafia, and had planned to fly to Spain with the main suspect for his murder, Andrei Lugovoi.
Mr Litvinenko's name made its way into infamy after he took tea with Mr Lugovoi and another Russian contact Dmitri Kovtun at a central London hotel on 1 November 2006.
He fell ill soon afterwards and spent the night vomiting.
Three days later he was admitted to Barnet General Hospital in north London, where his condition gradually became a cause for concern.
On 11 November he was interviewed by the BBC Russian Service and said he was in "very bad shape" after a "serious poisoning".
THE LITVINENKO CASE
- 1 Nov 2006 - Alexander Litvinenko has tea with former agents Andrei Lugovoi and Dmitri Kovtun in London
- 4 Nov 2006 - After three days of vomiting he is admitted to Barnet General Hospital
- 17 Nov 2006 - His condition worsens and he is transferred to University College Hospital
- 23 Nov 2006 - Litvinenko dies
- 24 Nov 2006 - His death is attributed to polonium-210
- 30 Nov 2006 - Home Secretary John Reid tells MPs traces of radioactivity had been discovered in 12 locations in London, as well as two British Airways planes.
- 4 Dec 2006 - Nine British detectives travel to Moscow to conduct inquiries
- 22 May 2007 - Britain's director of public prosecutions decides Mr Lugovoi should be charged with the murder of Mr Litvinenko
- 31 May 2007 - Mr Lugovoi denies any involvement in his death but says Mr Litvinenko was a British spy
- 5 Jul 2007 - Russia officially refuses to extradite Mr Lugovoi, saying its constitution does not allow it
- 16 Jul 2007 - Britain expels four Russian diplomats, and three days later Moscow retaliates by kicking out four British diplomats
- 20 Sept 2012 - Pre-inquest review hears that Russia's links to the death will be probed
- 13 Dec 2012 - Legal review told that Mr Litvinenko was a paid worker for MI6
During that same interview, Mr Litvinenko, a critic of the Putin regime, said he had been looking into the assassination of Russian journalist Anna Politkovskaya.
He said he would hand over documents he had received on 1 November to a Russian newspaper when he recovered.
But he never did. On 17 November he was transferred to University College Hospital in London after his condition worsened.
He died six days later, with his wife Marina, father Walter, and son Anatoli at his bedside.
Born in the city of Voronezh in 1962, Mr Litvinenko joined a military unit of the Soviet Union's interior ministry in 1980 and reportedly joined the KGB eight years later.
He rose to the rank of lieutenant-colonel when the KGB became the FSB in the 1990s.
Mr Putin was his ultimate boss at the FSB but they reportedly fell out.
After leaving the service Mr Litvinenko wrote a book, Blowing up Russia: Terror from Within, in which he claimed FSB agents had been responsible for the bombing of apartment blocks in Moscow and two other cities in 1999.
The bombings were blamed on Chechen separatists and his book claimed they were used as a pretext for the second Russian invasion of Chechnya.
Mr Litvinenko came to Britain in 2000 and obtained asylum.
After his death, suspicion fell on Mr Lugovoi and Mr Kovtun, the two Russians he had met for tea at the Millennium Hotel.
A post-mortem examination suggested Mr Litvinenko had died after being poisoned with the radioactive substance polonium-210.
A frantic police investigation led to a number of premises being briefly sealed off while forensic scientists tested for traces of the radioactive material.
Locations which tested positive included the Millennium Hotel, the Abracadabra lap-dancing club and the Emirates football stadium, where Mr Lugovoi had watched Arsenal play CSKA Moscow.
It also emerged he had met Italian academic Mario Scaramella at the Itsu sushi restaurant in central London, where he is said to have received documents about the death of Mrs Politkovskaya, a long-term critic of the FSB.
Traces were also found on two planes at Heathrow airport, at the British embassy in Moscow and at a flat in Hamburg, Germany, linked to Mr Kovtun.
Around 700 people had to be tested for radioactive poisoning but none was seriously ill.
After a two-month investigation, Scotland Yard detectives handed over a file to the then director of public prosecutions, Sir Ken Macdonald, who announced in May 2007 that he was recommending Mr Lugovoi be charged with murder.
Mr Lugovoi and Mr Kovtun both denied any responsibility for the death and at a news conference in Moscow Mr Lugovoi repeatedly stressed his innocence and claimed Mr Litvinenko was a British spy who might have been killed by the British security services.
The office of the prosecutor general in Moscow was quick to point out Mr Lugovoi could not and would not be extradited because the constitution prevented the extradition of Russian citizens.
In July 2007, Anglo-Russian tensions turned into an ugly spat with four Russian and four British diplomats expelled from their respective embassies.
Britain broke off links with the Russian security services and, although relations have thawed, David Cameron refused to renew links between MI6 and the FSB when he visited Moscow last year.
After pre-inquest reviews in September and December 2012, the date for the inquest into Mr Litvinenko's death was set at 1 May 2013.