Undoubtedly helped by the extensive CCTV  system which monitors movement around London, the British are making rapid progress in cracking the Litvinenko assassination.

• The assassins were so bungling that they dropped the polonium on the floor of a London hotel room, a senior government source told The Daily Telegraph yesterday.

• Scientists at the Atomic Weapons Establishment at Aldermaston are believed to have already identified the nuclear plant which made the polonium.

• Anti-terrorist officers at Scotland Yard believe the polonium was brought into London on a British Airways flight from Moscow on Oct 25, a week before Mr Litvinenko fell ill. [snip]

The trail of the alpha-radiation was so strong that detectives have been able to follow it across London.

The senior government source, who is aware of the discussions of the Cabinet's emergency committee, Cobra, said the picture of the killers that was emerging was closer to bungling assassins than cool James Bond-type killers.

Clear traces of the radiation were found on the floor of a room, thought to be in the Millennium hotel in central London, the source said, as well as on a light switch in the same room. The traces were so strong that they indicated the actual source of the radiation was present, not a secondary source such as excretions from Mr Litvinenko's contaminated body. Friends of Mr Litvinenko say that he did not visit the rooms in either of the hotels.

The potential political fall-out from the affair grew as it emerged that the Atomic Weapons Establishment can identify the plant at which the radioactive element was made and are in fact thought to have done so. If that is, as many suspect, in Russia, it could cause acute embarrassment to President Vladimir Putin's government because its head of nuclear security said recently that no similar material had gone missing in the country.