Russian state 'involved in spy's death' - British documents
13 December 2012 Last updated at 23:15 GMT
An official hearing into the murder of the former Russian spy, Alexander Litvinenko, has been told the government has evidence that Moscow was involved.
Mr Litvinenko died six years ago after he was poisoned with a radioactive substance.
Lawyers for his widow said that Britain had a duty to protect him because he was working for MI6 at the time.
The BBC's Security Correspondent, Gordon Corera, reports.