23 November 2006: Alexander Litvinenko dies in hospital

Alexander Litvinenko, the former Russian spy, came to London seeking political asylum. But on this day in 2006, he died in hospital after being poisoned with the radioactive isotope polonium-210. The accusations of murder which followed set back British-Russian relations, which had up till then been relatively amicable, more than 20 years.

Litvinenko joined the KGB in 1988, and gained promotion through the ranks of the Federal Security Service (FSB). He became closely involved with the Russian tycoon Boris Berezovsky, and in 1998 he claimed that one of his superiors had ordered Berezovsky's murder (Berezovsky was found hanged at his UK home in March 2013). Rather than following orders, Litvinenko told Berezovsky everything. He was dismissed from the FSB soon after, and eventually fled to London. This, Russia alleged, represented a defection to MI6.

On 1 November 2006, Litvinenko met KGB agent and Andrei Lugovoi (now a Russian politician) and his business partner, Dmitri Kovtun, at a hotel in Grosvenor Square, where Litvinenko sipped green tea. After the meeting, the three shook hands and parted. But Litvinenko was soon vomiting.

He had laid his accusation squarely at the Kremlin's door. "I want the world to see what they did to me", he said, publishing a photo of himself on his University College Hospital bed, his hair lost and his organs failing. His dying words to his father were "daddy, Putin has poisoned me".

Attempts by the British government to extradite the chief suspect, Lugovoi, (who continues to deny any responsibility for the murder) were rebuffed by Russia. This led to the tit-for-tat expulsion of diplomats by both countries.