The murder of former Russian agent Alexander Litvinenko was carried out with the backing of the Russian state, Whitehall sources have told the BBC.
A senior security official told Newsnight there were "very strong indications it was a state action". [...]
The BBC has been told that Russia's internal security organisation, the FSB, operated under Mr Putin with far more autonomy than the organisations usually entrusted with foreign espionage operations.
Our source said: "We very strongly believe the Litvinenko case to have had some state involvement."
Newsnight has also learned that officers at MI5 believe they thwarted an attempt last summer to kill another Russian dissident, Boris Berezovsky.
The BBC's source said the Berezovsky incident showed "continued FSB willingness to consider operations against people in the West". [...]
In November, head of MI5 Jonathan Evans expressed concern that there had been "no decrease" in the number of Russian covert intelligence officers operating in the UK since the end of the Cold War.
The service believes there are around 30 operating from Russian diplomatic missions here.
My personal opinion on why they killed Litvinenko was that it had something to do with what he knew about 9/11 and related Russian sponsorship of Islamic terrorism. Because it sure doesn't seem worth it to kill him over something like this, when no one outside of Russia seemed to care much. You can find a full archive of Russia-related posts here.