This murder - and it looks increasingly like a cunning, ruthless murder - has sparked a huge police investigation that has uncovered radiation at 12 sites across London and on two British Airways planes that had flown between London and Moscow.(snip)

The Sunday Times has established that a former Russian agent called Andrei Lugovoi, who was known to Litvinenko, stayed in the hotel in the days before November 1 and that he is - he says - significantly contaminated with polonium.

Litvinenko's close friends believe Lugovoi is deeply involved, either knowingly or unknowingly, in the poisoning. But Lugovoi and his business partner, Dimitri Kovtun, who also visited London, vehemently deny involvement and say they have been set up as fall guys. (snip)

Police have checked this vehicle and found contamination. Litvinenko, it seems, had been poisoned sometime between leaving home that morning and driving back.

A source close to the investigation said: "This is a very complex John Le Carré-style situation, but we are pretty confident that we will get there."