When a Russian dissident was poisoned in London with a highly radioactive substance, the UK government accused the Kremlin of his murder.
Alexander Litvinenko had been a colonel in the Russian security services, but claimed the Putin government was corrupt.
In November 2006 he suffered an excruciating death after he was poisoned with Polonium 210. His wife Marina was at his bedside.
Witness: The stories of our times told by the people who were there.